LU-14214 ofd: fix locking in ofd_object_fallocate()

LU-14214 ofd: fix locking in ofd_object_fallocate()

the rule is that locks are taken after transaction start.

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I5252be0033611f03b355c1f98e21422cdde55c9e
Reviewed-on: https://review.whamcloud.com/40969
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>