staging: lustre: mdc: Make IT_OPEN take lookup bits lock

An earlier commit accidentally changed handling of IT_OPEN,
making it take the MDS_INODELOCK_UPDATE bits lock instead of
MDS_INODELOCK_LOOKUP. This does not cause any known bugs.

Signed-off-by: Patrick Farrell <paf@cray.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8842
Reviewed-on: https://review.whamcloud.com/23797


Fixes: 70a251f6 ("staging: lustre: obd: decruft md_enqueue() and md_intent_lock()"
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>