Add Junit4 to the classpath for CollectAllTests

This is needed for CollectAllTests to work with Junit4 tests.

Change-Id: I5e339022220b8e40bcb12337a09f3615dad7d53c
Merge "Add Junit4 to the classpath for CollectAllTests"
Merge branch 'master' of https://android.googlesource.com/platform/build