Merge pull request #5698 from tchaikov/wip-12638-firefly

mon: add a cache layer over MonitorDBStore

Reviewed-by: Loic Dachary <ldachary@redhat.com>

diff --cc src/common/config_opts.h
Simple merge

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

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