Fixes failed tests in PackageManagerTests

- #testDeleteNormalInternalRetainData
  Removes the check for the directory. Test does not have
  the access right of the data folder of other packages.

- #testIsSignedBy
  Updates the correct public key for key set A.

Bug: 152007236
Test: atest PackageManagerTests
Change-Id: I4adbf5e1d321e7f4ed9f1005ec52eb1ea3d04c27