LU-8369 nodemap: ignore loopback NID when classifying

LU-8369 nodemap: ignore loopback NID when classifying

The loopback NID doesn't make sense in the nid range system
currently used by nodemap. In order to add the MGS to a nodemap,
this patch modifies nodemap_classify_nid to use the first non-lo nid
if it is given the loopback nid.

Signed-off-by: Kit Westneat <kit.westneat@gmail.com>
Change-Id: Iea91a54a14021e478782eedb28ae1a6c3e62d38c
Reviewed-on: http://review.whamcloud.com/21160
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>