LU-1187 mdt: Only create remote dir on MDT0

LU-1187 mdt: Only create remote dir on MDT0

1.Add checking for only creating remote dir on MDT0.
2.Add enable_remote_dir parameter to enalbe remote dir creation
on other MDTs.

Change-Id: I272d4763f07115c5aa0432eb4bbdda5349711d25
Signed-off-by: Wang Di <di.wang@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/4336
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>