LU-4320 mdt: fixup MDS_SWAP_LAYOUTS ELC handling

LU-4320 mdt: fixup MDS_SWAP_LAYOUTS ELC handling

In mdc_ioc_swap_layouts() cancel *any* unused locks with LAYOUT or
XATTR IBITS set on the two files. (This matches the locks acquired in
mdt_swap_layouts(). Previously only locks that conflicted with a CR
LAYOUT lock were cancelled.) Add HABEO_CLAVIS to the target handler
flags for MDS_SWAP_LAYOUTS and call ldlm_request_cancel() from
mdt_swap_layouts() to do the intended early lock cancellation before
the handler acquires its own locks.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I9d7ba9ac660b136dafa7e307177b92204a1257c3
Reviewed-on: http://review.whamcloud.com/9329
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Faccini Bruno <bruno.faccini@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>