Fix incompatible APK container signature

Somehow this issue is only reproducible on TH.

In the pushTestApex() method, buildHelper.getTestFile()
will reference a file like:
/tmp/tf-workfolder10675344980669124774/tests-zip_4606121987780006706/host/testcases/StagedRollbackTest/test.rebootless_apex_v1.apex

while installPackage(REBOOTLESS_V2) will reference a file like:
/tmp/tf-workfolder10675344980669124774/tests-zip_4606121987780006706/target/testcases/ApexTestCases/x86_64/test.rebootless_apex_v2.apex

Those 2 files have incompatible signatures.

This CL ensures both v1 and v2 are accessed by buildHelper.getTestFile()
so they have compatible signatures.

Bug: 242639590
Test: atest StagedInstallInternalTest
Change-Id: I8dfafa5754b714867e0c60f7ccb8689c9471da01