LU-1582 tests: do not force sync before failover

LU-1582 tests: do not force sync before failover

Commit 17a69cf25ed0991e04d85c259f4294dc59734e1e forced sync on every
target on a facet before it was failed, in order to fix failures in
recovery-small.sh test_105() due to initial client connect failing.
This was causing local-node testing to hang in replay-ost-single.sh
test_8b() because the client mountpoint was being sync'd and would
never finish due to a fail_loc preventing any RPCs from completing.

Syncing the targets before failover also defeats the purpose of many
recovery tests.  Instead, recovery-small test_105 creates a file on
the to-be-failed OST and writes to it, to trigger the exp_need_sync
and commit the new client export, without incorrectly forcing every
OST to be sync'd for every test that is using facet_failover().

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ied5f2ecf1f6523d4163916b24e5c4281902d500c
Reviewed-on: http://review.whamcloud.com/3239
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@whamcloud.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>