LU-10070 ldlm: layout lock fixes

LU-10070 ldlm: layout lock fixes

as the intent_layout operation becomes more frequent with SEL,
cancel existent layout locks in advance and reuse ELC to deliver
cancels to MDS

as clients are given LCK_EX layout locks, take into account this
mode as well in ldlm_lock_match

Cray-bug-id: LUS-2528
Signed-off-by: Vitaly Fertman <c17818@cray.com>
Change-Id: I1525153b3a07385fc17ef5416ded7b6d4378b2ec
Reviewed-on: https://review.whamcloud.com/35232
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>