Minor java code cleanup

[ajayk]

Issue #, if available:

Description of changes:
Update Compiler and Surefire Plugin
Basic Java cleanup

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[SalusaSecondus]

Thank you for this PR. We'll look through it.

test failures

[bdonlan]

These changes break the tests:

$ JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_192.jdk/Contents/Home mvn test -Pfast-tests-only
[INFO] Scanning for projects...
[INFO]
[INFO] ---------------< com.amazonaws:aws-encryption-sdk-java >----------------
[INFO] Building aws-encryption-sdk-java 1.3.6-SNAPSHOT
[INFO] --------------------------------[ jar ]---------------------------------
[INFO]
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ aws-encryption-sdk-java ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/bdonlan/sdkjava/aws-encryption-sdk-java/src/main/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.8.0:compile (default-compile) @ aws-encryption-sdk-java ---
[INFO] Changes detected - recompiling the module!
[INFO] Compiling 67 source files to /Users/bdonlan/sdkjava/aws-encryption-sdk-java/target/classes
[INFO] /Users/bdonlan/sdkjava/aws-encryption-sdk-java/src/main/java/com/amazonaws/encryptionsdk/AwsCrypto.java: Some input files use unchecked or unsafe operations.
[INFO] /Users/bdonlan/sdkjava/aws-encryption-sdk-java/src/main/java/com/amazonaws/encryptionsdk/AwsCrypto.java: Recompile with -Xlint:unchecked for details.
[INFO]
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ aws-encryption-sdk-java ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory /Users/bdonlan/sdkjava/aws-encryption-sdk-java/src/test/resources
[INFO]
[INFO] --- maven-compiler-plugin:3.8.0:testCompile (default-testCompile) @ aws-encryption-sdk-java ---
[INFO] Nothing to compile - all classes are up to date
[INFO]
[INFO] --- maven-surefire-plugin:2.22.0:test (default-test) @ aws-encryption-sdk-java ---
[INFO]
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running com.amazonaws.encryptionsdk.FastTestsOnlySuite
[ERROR] Tests run: 2001, Failures: 0, Errors: 4, Skipped: 0, Time elapsed: 27.486 s <<< FAILURE! - in com.amazonaws.encryptionsdk.FastTestsOnlySuite
[ERROR] contextWithInvalidCharacters(com.amazonaws.encryptionsdk.internal.EncContextSerializerTest)  Time elapsed: 0.006 s  <<< ERROR!
java.lang.Exception: Unexpected exception, expected<java.lang.IllegalArgumentException> but was<java.lang.NoSuchMethodError>
	at com.amazonaws.encryptionsdk.internal.EncContextSerializerTest.contextWithInvalidCharacters(EncContextSerializerTest.java:365)

[ERROR] testGrantTokenPassthrough_usingMKsetCall(com.amazonaws.encryptionsdk.kms.KMSProviderBuilderMockTests)  Time elapsed: 0.031 s  <<< ERROR!
java.lang.NoSuchMethodError: java.nio.ByteBuffer.rewind()Ljava/nio/ByteBuffer;
	at com.amazonaws.encryptionsdk.kms.KMSProviderBuilderMockTests.testGrantTokenPassthrough_usingMKsetCall(KMSProviderBuilderMockTests.java:122)

[ERROR] testUserAgentPassthrough(com.amazonaws.encryptionsdk.kms.KMSProviderBuilderMockTests)  Time elapsed: 0.017 s  <<< ERROR!
java.lang.NoSuchMethodError: java.nio.ByteBuffer.rewind()Ljava/nio/ByteBuffer;
	at com.amazonaws.encryptionsdk.kms.KMSProviderBuilderMockTests.testUserAgentPassthrough(KMSProviderBuilderMockTests.java:220)

[ERROR] testGrantTokenPassthrough_usingMKPWithers(com.amazonaws.encryptionsdk.kms.KMSProviderBuilderMockTests)  Time elapsed: 0.01 s  <<< ERROR!
java.lang.NoSuchMethodError: java.nio.ByteBuffer.rewind()Ljava/nio/ByteBuffer;
	at com.amazonaws.encryptionsdk.kms.KMSProviderBuilderMockTests.testGrantTokenPassthrough_usingMKPWithers(KMSProviderBuilderMockTests.java:170)

[INFO]
[INFO] Results:
[INFO]
[ERROR] Errors:
[ERROR]   EncContextSerializerTest.contextWithInvalidCharacters »  Unexpected exception,...
[ERROR]   KMSProviderBuilderMockTests.testGrantTokenPassthrough_usingMKPWithers:170 » NoSuchMethod
[ERROR]   KMSProviderBuilderMockTests.testGrantTokenPassthrough_usingMKsetCall:122 » NoSuchMethod
[ERROR]   KMSProviderBuilderMockTests.testUserAgentPassthrough:220 » NoSuchMethod java.n...
[INFO]
[ERROR] Tests run: 2001, Failures: 0, Errors: 4, Skipped: 0
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 35.131 s
[INFO] Finished at: 2018-10-22T10:52:22-07:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.22.0:test (default-test) on project aws-encryption-sdk-java: There are test failures.
[ERROR]
[ERROR] Please refer to /Users/bdonlan/sdkjava/aws-encryption-sdk-java/target/surefire-reports for the individual test results.
[ERROR] Please refer to dump files (if any exist) [date]-jvmRun[N].dump, [date].dumpstream and [date]-jvmRun[N].dumpstream.
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/MojoFailureException

[bdonlan]

Nevermind, looks like it was an unclean build. Approving.