Merge branch 'stable-2.7'

* stable-2.7:
  Fix: failed to validate Change-Id of some new patch-sets pushed by 'refs/changes'

Conflicts:
	gerrit-server/src/main/java/com/google/gerrit/server/ChangeUtil.java
	gerrit-server/src/main/java/com/google/gerrit/server/git/validators/CommitValidators.java

Change-Id: I89ffdf132ad320215b00d0628c07797157a1b925