LU-5092 nodemap: convert member hash to a list

LU-5092 nodemap: convert member hash to a list

The members of a nodemap were stored in a hash, but they were only
iterated against, not accessed by key. This patch converts the hash
to a list in order to simplify things.

Signed-off-by: Kit Westneat <kit.westneat@gmail.com>
Change-Id: Ic1df4035d1c53a7c7966c4c528d20cefc7258d0e
Reviewed-on: http://review.whamcloud.com/14885
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>