LU-8397 mgc: add comma-separated nids for primary MGS

LU-8397 mgc: add comma-separated nids for primary MGS

In lustre_start_mgc(), if the primary MGS has multiple nids separated by
commas, then only the first nid is added, and the other nids are not added.
This patch fixes the above issue by adding the nids until the end of the
primary MGS nid list or hitting the first failover MGS nid.

Test-Parameters: combinedmdsmgs=false envdefinitions=ONLY=77 testlist=conf-sanity
Test-Parameters: envdefinitions=ONLY=77 testlist=conf-sanity

Signed-off-by: Vladimir Saveliev <vladimir.saveliev@seagate.com>
Signed-off-by: Jian Yu <jian.yu@intel.com>
Seagate-bug-id: MRP-2930
Change-Id: I3e84786bfc08767c75a133affb4f86325d789d6e
Reviewed-on: https://review.whamcloud.com/21308
Tested-by: Jenkins
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Emoly Liu <emoly.liu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>