Merge branch 'stable-2.7'

* stable-2.7:
  Fix compilation failure in RefControlTest
  Verify access to source ref during add branch operation

Conflicts:
	gerrit-server/src/main/java/com/google/gerrit/server/project/ProjectControl.java
	gerrit-server/src/test/java/com/google/gerrit/server/project/RefControlTest.java

Change-Id: I05be78df8d2717105146e7f285e092598756fff0