mon: trigger transaction on MDS health changes

I think this was previously only working as a side effect
of other MDS map changes.

Signed-off-by: John Spray <john.spray@redhat.com>
client: failure injection for cap release

Used for simulating a buggy client that trips
the error detection in #9282 (warn clients
which aren't revoking caps)

Signed-off-by: John Spray <john.spray@redhat.com>
xlist: implement const_iterator

Signed-off-by: John Spray <john.spray@redhat.com>
mds: health metric for late releasing caps

Follow up on Yan Zheng's "mds: warn clients which
aren't revoking cap" to include a health metric
for this condition as well as the clog messages.

Signed-off-by: John Spray <john.spray@redhat.com>
client: fix trim_caps for inodes in root

Previously client would fail to release caps for files
in the root directory in response to CEPH_SESSION_RECALL_STATE
messages.

Signed-off-by: John Spray <john.spray@redhat.com>