LU-1842 quota: don't setup qsd for standalone MGS

LU-1842 quota: don't setup qsd for standalone MGS

Only set up the qsd instance if the associated target is either a MDT
or a OST. We typically have no interest in setting up a QSD instance
on a standalone MGS.

Signed-off-by: Johann Lombardi <johann.lombardi@intel.com>
Change-Id: I0facb08feef0b36f141b749d7be538cbde5f1114
Reviewed-on: http://review.whamcloud.com/4203
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Niu Yawei <niu@whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>