Merge branch 'stable-2.9' into stable-2.10

Conflicts:
	gerrit-server/src/main/java/com/google/gerrit/server/git/SubmoduleOp.java
	gerrit-server/src/main/java/com/google/gerrit/server/git/strategy/RebaseIfNecessary.java
	gerrit-server/src/main/java/com/google/gerrit/server/git/strategy/SubmitStrategyFactory.java

Change-Id: Id716ae24401756b9cfbcb46489259c0d9660412a