Bug 8606: Continue leadership transfer on pauseLeader timeout

Modified it to continue with leadership transfer if pauseLeader times out
instead of aborting. The shard may have a lot of transactions queued up
which it can't finish in time but there may still be a follower that is
caught up (ie whose matchIndex equals the leader's lastIndex) or would be
caught up if leadership transfer continued. Worst case is no follower is
available and the "catch up" phase of leadership transfer also times out
which would lengthen shut down time but that should be fine.

Change-Id: I1ec1ef43bb556e50416bb7239ce3c267265db9b3
Signed-off-by: Tom Pantelis <tompantelis@gmail.com>