Merge pull request #53340 from trociny/wip-62724-reef

reef: mds: optionally forbid to use standby for another fs as last resort

Reviewed-by: Leonid Usov <leonid.usov@ibm.com>
Reviewed-by: Rishabh Dave <ridave@redhat.com>
Reviewed-by: Venky Shankar <vshankar@redhat.com>

diff --cc PendingReleaseNotes
Simple merge

diff --cc src/common/options/mds.yaml.in
Simple merge

diff --cc src/mds/Server.cc
Simple merge