Fix race condition for jdiff/apicheck

Some build breakages happening on git_master/docs because jdiff rule and
apicheck rule may start in the same time, and jdiff may delete the same
srcjars and out dirs when apicheck trying to read which can cause
apicheck to be failed.

So change the dir names used by jdiff to not mix with dirs used by
apicheck.

Test: m -j docs
Bug: b/114368000
Change-Id: I90a53e0ef5f1ff947db7eb8cc73744919a9b93cb