Fix: push bypass review cannot close change from UI

Push bypass review cannot close the change from UI automatically when this change's
current patchset is also the current patchset of another change on the same branch of
the same project, and the other change has already been closed, e.g. Abandoned.

The reason is in ReceiveCommits.changeRefsById() the patchset's revison is used as key
of the result(HashMap), when the key has more than one value(change ref) only the last
one is kept, the others are covered.

This commit fix it by replacing the HashMap with HashMultimap.

Bug: Issue 1933
Change-Id: I6fb37bb9b2b6ec45bde0342c503d95277a94768a
1 file changed