Merge PR #20760 into wip-sage-testing-20180407.023110

* refs/pull/20760/head:
	mon/ConfigMonitor: add 'config reset' command
	mon/ConfigMonitor: add 'config log' command
	mon/ConfigMap: add ConfigChangeSet
	mon/ConfigMonitor: avoid no-op updates
	mon/ConfigMonitor: maintain history of all config changes

diff --cc src/mon/ConfigMonitor.cc
Simple merge

diff --cc src/mon/MonCommands.h
Simple merge