Small bugs in test cases

[JaySon-Huang]

Bug Report

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1. Minimal reproduce step (Required)

2. What did you expect to see? (Required)

3. What did you see instead (Required)

[452/990] PageFileTest.PageFileLink (2893 ms)
[2022/03/01 15:57:38.362 +08:00] [INFO] [PathCapacityMetrics.cpp:70] ["PathCapacityMetrics:Init capacity [path=/tiflash/tmp/] [capacity=0.00 B]"] [thread_id=1]
[2022/03/01 15:57:38.405 +08:00] [INFO] [<unknown>] ["RegionPersister:RegionPersister running in normal mode"] [thread_id=1]
[2022/03/01 15:57:38.405 +08:00] [INFO] [PageStorage.cpp:186] ["PageStorage:RegionPersister begin to restore data from disk. [path=/tiflash/tmp/kvstore] [num_writers=4]"] [thread_id=1]
[2022/03/01 15:57:38.406 +08:00] [INFO] [PageStorage.cpp:340] ["PageStorage:RegionPersister restore 0 pages, write batch sequence: 0, 0 puts and 0 refs and 0 deletes and 0 upserts"] [thread_id=1]
[2022/03/01 15:57:38.406 +08:00] [INFO] [KVStore.cpp:45] ["KVStore:Restored 0 regions"] [thread_id=1]
[2022/03/01 15:57:38.407 +08:00] [INFO] [<unknown>] ["RegionTable:Start to restore"] [thread_id=1]
[2022/03/01 15:57:38.407 +08:00] [INFO] [<unknown>] ["RegionTable:Restore 0 tables"] [thread_id=1]
�[0;33mNote: Google Test filter = PageFileTest.PageFileLink
�[m�[0;32m[==========] �[mRunning 1 test from 1 test case.
�[0;32m[----------] �[mGlobal test environment set-up.
�[0;32m[----------] �[m1 test from PageFileTest
�[0;32m[ RUN      ] �[mPageFileTest.PageFileLink
=================================================================
==18196==ERROR: AddressSanitizer: stack-use-after-scope on address 0x7ffe811fe3a0 at pc 0x0000058fd377 bp 0x7ffe811fd690 sp 0x7ffe811fce58
READ of size 1024 at 0x7ffe811fe3a0 thread T0
    #0 0x58fd376 in __asan_memcpy /llvm-project/compiler-rt/lib/asan/asan_interceptors_memintrinsics.cpp:22:3
    #1 0x5a82865 in DB::ReadBuffer::read(char*, unsigned long) /home/jenkins/agent/workspace/tiflash-sanitizer-daily/tics/dbms/src/IO/ReadBuffer.h:135:13
    #2 0x5a82865 in DB::ReadBuffer::readStrict(char*, unsigned long) /home/jenkins/agent/workspace/tiflash-sanitizer-daily/tics/dbms/src/IO/ReadBuffer.h:146:18
    #3 0xcb77e4e in DB::PS::V2::PageMetaFormat::genWriteData(DB::WriteBatch&, DB::PS::V2::PageFile&, DB::PS::V2::PageEntriesEdit&) /home/jenkins/agent/workspace/tiflash-sanitizer-daily/tics/dbms/src/Storages/Page/V2/PageFile.cpp:147:36
    #4 0xcb8974c in DB::PS::V2::PageFile::Writer::write(DB::WriteBatch&, DB::PS::V2::PageEntriesEdit&, std::__1::shared_ptr<DB::WriteLimiter> const&) /home/jenkins/agent/workspace/tiflash-sanitizer-daily/tics/dbms/src/Storages/Page/V2/PageFile.cpp:755:36
    #5 0x91a673c in DB::PS::V2::tests::PageFileTest_PageFileLink_Test::TestBody() /home/jenkins/agent/workspace/tiflash-sanitizer-daily/tics/dbms/src/Storages/Page/V2/tests/gtest_page_file.cpp:196:5
...

Address 0x7ffe811fe3a0 is located in stack of thread T0 at offset 448 in frame
    #0 0x91a4a4f in DB::PS::V2::tests::PageFileTest_PageFileLink_Test::TestBody() /home/jenkins/agent/workspace/tiflash-sanitizer-daily/tics/dbms/src/Storages/Page/V2/tests/gtest_page_file.cpp:166
...
...
[452/990] PageFileTest.PageFileLink returned/aborted with exit code 1 (2893 ms)

https://github.com/pingcap/tics/blob/4954a24c0f15f9327fff1591778cd61c64b8e8dd/dbms/src/Storages/Page/V2/tests/gtest_page_file.cpp#L177-L192
https://github.com/pingcap/tics/blob/4954a24c0f15f9327fff1591778cd61c64b8e8dd/dbms/src/Storages/Page/V2/tests/gtest_page_file.cpp#L228-L243

c_buff1, c_buff2 use after scoped

4. What is your TiFlash version? (Required)