LU-617 temporary fix for the setattr from open

LU-617 temporary fix for the setattr from open

The setattr from open(open(O_TRUNC)) is serialized with
'cl_setattr_lock' on client and goes to a dedicate portal, which is
different with other reint operations, consequently, setattr RPC
can be parallel with other reint RPCs, and that result in the race of
updating last_transno/last_xid on server.

This temporary fix removes the LASSERT(req_is_replay(req)) in
mdt_last_rcvd_update().

Signed-off-by: Niu Yawei <niu@whamcloud.com>
Change-Id: I7e07eaf9e718c2d75d9a503207523be9c700ea4a
Reviewed-on: http://review.whamcloud.com/1295
Tested-by: Hudson
Reviewed-by: Mikhail Pershin <tappro@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>