Merge pull request #18595 from batrick/mon-clock

mon: a few conversions to monotonic clock

Reviewed-by: Adam C. Emerson <aemerson@redhat.com>
Reviewed-by: Sage Weil <sage@redhat.com>
Reviewed-by: Kefu Chai <kchai@redhat.com>

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

diff --cc src/osd/OSD.cc
Simple merge