LU-8297 obd: release MGC device if connect fails

LU-8297 obd: release MGC device if connect fails

In lustre_fill_super() if lustre_start_mgc() fails then call
lustre_common_put_super() to release a reference on the MGC device
attached to the LSI.

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: I89697badac971e78e1cd3596e7ffc42afdcbfeee
Reviewed-on: http://review.whamcloud.com/20851
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>