LU-5092 nodemap: handle config changes while mid-flight

LU-5092 nodemap: handle config changes while mid-flight

This adds the ability to detect when the nodemap configuration has
changed between messages for very large configurations. If the
configuration is over 1MB (about 25k entries), it needs to be sent
in multiple messages. If the configuration changes in-between these
messages, then the client needs to abort the previous get config
operation and restart.

Test-Parameters: envdefinitions=SLOW=yes testlist=sanity-sec
Signed-off-by: Kit Westneat <kit.westneat@gmail.com>
Change-Id: I2bf6e4bade947fea8331c2922d9c33ab49100577
Reviewed-on: http://review.whamcloud.com/16941
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>