resource/aws_db_instance: Prevent double apply for snapshot_identifie…

…r with multiple other arguments

* backup_retention_period
* backup_window
* iam_database_authentication_enabled
* maintenance_window
* monitoring_interval
* monitoring_role_arn
* parameter_group_name

Previously:

```
--- FAIL: TestAccAWSDBInstance_SnapshotIdentifier_BackupRetentionPeriod (1154.50s)
	testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'backup_retention_period' expected "1", got "0"
--- FAIL: TestAccAWSDBInstance_SnapshotIdentifier_BackupWindow (1195.82s)
	testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'backup_window' expected "00:00-08:00", got "06:13-06:43"
--- FAIL: TestAccAWSDBInstance_SnapshotIdentifier_IamDatabaseAuthenticationEnabled (1113.22s)
	testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'iam_database_authentication_enabled' expected "true", got "false"
--- FAIL: TestAccAWSDBInstance_SnapshotIdentifier_MaintenanceWindow (1259.26s)
	testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'maintenance_window' expected "Sun:01:00-Sun:01:30", got "wed:10:33-wed:11:03"
--- FAIL: TestAccAWSDBInstance_SnapshotIdentifier_Monitoring (1214.60s)
	testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'monitoring_interval' expected "5", got "0"
--- FAIL: TestAccAWSDBInstance_SnapshotIdentifier_ParameterGroupName (1134.54s)
	testing.go:527: Step 0 error: Check failed: Check 4/4 error: aws_db_instance.test: Attribute 'parameter_group_name' expected "tf-acc-test-4546585708384390733", got "default.mariadb10.2"
```

aws/resource_aws_db_instance.go

@@ -672,13 +672,13 @@ func resourceAwsDbInstanceCreate(d *schema.ResourceData, meta interface{}) error
 		var requiresModifyDbInstance bool
 
 		opts := rds.RestoreDBInstanceFromDBSnapshotInput{
+			AutoMinorVersionUpgrade: aws.Bool(d.Get("auto_minor_version_upgrade").(bool)),
+			CopyTagsToSnapshot:      aws.Bool(d.Get("copy_tags_to_snapshot").(bool)),
 			DBInstanceClass:         aws.String(d.Get("instance_class").(string)),
 			DBInstanceIdentifier:    aws.String(d.Get("identifier").(string)),
 			DBSnapshotIdentifier:    aws.String(d.Get("snapshot_identifier").(string)),
-			AutoMinorVersionUpgrade: aws.Bool(d.Get("auto_minor_version_upgrade").(bool)),
 			PubliclyAccessible:      aws.Bool(d.Get("publicly_accessible").(bool)),
 			Tags:                    tags,
-			CopyTagsToSnapshot:      aws.Bool(d.Get("copy_tags_to_snapshot").(bool)),
 		}
 
 		if attr, ok := d.GetOk("name"); ok {
@@ -696,6 +696,14 @@ func resourceAwsDbInstanceCreate(d *schema.ResourceData, meta interface{}) error
 			opts.AvailabilityZone = aws.String(attr.(string))
 		}
 
+		if _, ok := d.GetOk("backup_retention_period"); ok {
+			requiresModifyDbInstance = true
+		}
+
+		if _, ok := d.GetOk("backup_window"); ok {
+			requiresModifyDbInstance = true
+		}
+
 		if attr, ok := d.GetOk("db_subnet_group_name"); ok {
 			opts.DBSubnetGroupName = aws.String(attr.(string))
 		}
@@ -708,6 +716,10 @@ func resourceAwsDbInstanceCreate(d *schema.ResourceData, meta interface{}) error
 			opts.Engine = aws.String(attr.(string))
 		}
 
+		if _, ok := d.GetOk("iam_database_authentication_enabled"); ok {
+			requiresModifyDbInstance = true
+		}
+
 		if attr, ok := d.GetOk("iops"); ok {
 			opts.Iops = aws.Int64(int64(attr.(int)))
 		}
@@ -716,6 +728,18 @@ func resourceAwsDbInstanceCreate(d *schema.ResourceData, meta interface{}) error
 			opts.LicenseModel = aws.String(attr.(string))
 		}
 
+		if _, ok := d.GetOk("maintenance_window"); ok {
+			requiresModifyDbInstance = true
+		}
+
+		if _, ok := d.GetOk("monitoring_interval"); ok {
+			requiresModifyDbInstance = true
+		}
+
+		if _, ok := d.GetOk("monitoring_role_arn"); ok {
+			requiresModifyDbInstance = true
+		}
+
 		if attr, ok := d.GetOk("multi_az"); ok {
 			// When using SQL Server engine with MultiAZ enabled, its not
 			// possible to immediately enable mirroring since
@@ -732,7 +756,10 @@ func resourceAwsDbInstanceCreate(d *schema.ResourceData, meta interface{}) error
 
 		if attr, ok := d.GetOk("option_group_name"); ok {
 			opts.OptionGroupName = aws.String(attr.(string))
+		}
 
+		if _, ok := d.GetOk("parameter_group_name"); ok {
+			requiresModifyDbInstance = true
 		}
 
 		if _, ok := d.GetOk("password"); ok {