LU-2824 mds: do not deactivate OSC if osc_create returns -EBUSY

During MDS<->OST orphan recovery, osc_create() will likely return
-EBUSY while OSCC_FLAG_SYNC_IN_PROGRESS flag is still set
due to slow ll_mdt service thread. The __mds_lov_synchronize() will
then deactivate the OSC, which will cause mds_create_objects() get
-EIO error.

This patch fixes the above issue by checking the return value of
mds_lov_clear_orphans(). If it's -EBUSY, then do not mark the
OSC as inactive.

Test-Parameters: envdefinitions=DURATION=21600 \
clientdistro=el5 serverdistro=el5 clientarch=x86_64 \
serverarch=x86_64 clientcount=4 osscount=2 mdscount=2 \
austeroptions=-R failover=true \
useiscsi=true testlist=recovery-mds-scale

Signed-off-by: Jian Yu <jian.yu@intel.com>
Change-Id: I7e04648524714999bbd72d730d1d618239b630e6
Reviewed-on: http://review.whamcloud.com/5450
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Tested-by: Hudson