Fix edit patrolling in multi Diffs

In multi diffs we had a "wrong" value for rc_last_oldid
set (not the directly previous revision but the one
selected by the user). Due to that there weren't any
unpatrolled recentchanges rows found. As that is cached
in memcached these rows stay unpatrollable forever.

Bug: 49019
Change-Id: I5d6111032dba7d102e30d85718639697f44c036e
(cherry picked from commit aa0308e3b901c28d4a5e63d1b93b999bde65e6ee)