LU-7433 ldlm: xattr locks are lost on mdt

LU-7433 ldlm: xattr locks are lost on mdt

mdt_intent_getxattr() can return EFAULT if a buffer cannot be found,
it is returned after lock_replace, where a new lock is installed into
lockp. An error forces ldlm_lock_enqueue() to destroy the original
lock, but ldlm_handle_enqueue0() drops the reference on the new lock.
xattr client code implied intent error is returned under a lock,
which is immediately cancelled. Check if a lock obtained and cancel
it properly for error cases. Note: we should support both cases for
interop needs, an intent error under a lock and with a lock abort.
Keep returning a lock with an intent error for interop purposes for
now, to be dropped later when client will get old enough.
make all intent ops to work through md_intent_lock: getxattr
and layout, which should extract the intent error.

Signed-off-by: Vitaly Fertman <vitaly.fertman@seagate.com>
Change-Id: I7b628b50448c4bdb26a3a8758fc16a44212ad9ac
Seagate-bug-id: MRP-3072 MRP-3137
Reviewed-by: Andrew Perepechko <andrew.perepechko@seagate.com>
Reviewed-by: Andriy Skulysh <andriy.skulysh@seagate.com>
Tested-by: Elena V. Gryaznova <elena.gryaznova@seagate.com>
Reviewed-on: http://review.whamcloud.com/17220
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
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>