staging: lustre: ptlrpc: add OBD_CONNECT_UNLINK_CLOSE flag

Add OBD_CONNECT_UNLINK_CLOSE flag for interop, once this is supported,
client packs file handle in unlink RPC, and MDT will close file before
unlink.

Signed-off-by: Lai Siyao <lai.siyao@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4367
Reviewed-on: http://review.whamcloud.com/10426


Reviewed-by: Andreas Dilger <andreas.dilger@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>