libprofile: Clear method bitmap padding bits.

Explicitly clear padding bits instead of zero-initializing
the entire buffer.

Test: atest com.android.cts.dexmetadata.InstallDexMetadataHostTest#testProfileSnapshotAfterInstall
Bug: 201627008
Change-Id: I31655e053f405a8d2903fb7b2e8e7176f5344226
1 file changed