LU-4843 mdt: Add OBD_CONNECT_DIR_STRIPE flag

LU-4843 mdt: Add OBD_CONNECT_DIR_STRIPE flag

Add OBD_CONNECT_DIR_STRIPE to tell if the client supports
striped dir, so only new client (>= 2.6) can access striped
directory.

Change-Id: I5d5f1a6a9f5efdce0c6fe22106a8853cd78bb486
Signed-off-by: Wang Di <di.wang@intel.com>
Reviewed-on: http://review.whamcloud.com/10773
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Bob Glossman <bob.glossman@intel.com>