MB-11462 Stop leftover upr streams when compactor restarts updater

If the compactor has finished and verifies that it has caught up
already and the currently running updater hasn't completed update of
current delta, it stops the current updater and switches to the compacted
index file. It has to clear active upr streams after stopping updater process.

Change-Id: I8609cb241748c2c5f04518995cdcbd2f806efc54
Reviewed-on: http://review.couchbase.org/38644
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: buildbot <build@couchbase.com>