LU-11056 lwp: fix lwp reconnection issue

LU-11056 lwp: fix lwp reconnection issue

After the OST or MDT was restarted, the lwp reconnection can be
failed for -EALREADY because the connect count in the connecttion
request is less then the value saved in the corresponding export
at MDT0000, which could cause the system hang.

The patch also changes lustre_lwp_connect to use OBD_CONNECT_MDS_MDS
flag only when the connection is between MDTs.

Change-Id: I9ae7b4faadc65fdaa78458a06315b1739d144feb
Signed-off-by: Hongchao Zhang <hongchao.zhang@intel.com>
Reviewed-on: https://review.whamcloud.com/32536
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>