+++ This bug was initially created as a clone of Bug #2280743 +++

Description of problem:
test_dumpfs passed but it shows below 
2024-03-20T21:38:38.702 INFO:tasks.ceph.mgr.x.smithi007.stderr:Exception in thread Thread-3:
2024-03-20T21:38:38.702 INFO:tasks.ceph.mgr.x.smithi007.stderr:Traceback (most recent call last):
2024-03-20T21:38:38.702 INFO:tasks.ceph.mgr.x.smithi007.stderr:  File "/usr/lib64/python3.9/threading.py", line 980, in _bootstrap_inner
2024-03-20T21:38:38.704 DEBUG:teuthology.orchestra.run.smithi007:> sudo adjust-ulimits ceph-coverage /home/ubuntu/cephtest/archive/coverage timeout 120 ceph --cluster ceph osd pool get cephfs_data pg_num
2024-03-20T21:38:38.712 INFO:tasks.ceph.mgr.x.smithi007.stderr:    self.run()
2024-03-20T21:38:38.712 INFO:tasks.ceph.mgr.x.smithi007.stderr:  File "/usr/lib64/python3.9/threading.py", line 1306, in run
2024-03-20T21:38:38.712 INFO:tasks.ceph.mgr.x.smithi007.stderr:    self.function(*self.args, **self.kwargs)
2024-03-20T21:38:38.712 INFO:tasks.ceph.mgr.x.smithi007.stderr:  File "/usr/share/ceph/mgr/stats/fs/perf_stats.py", line 222, in re_register_queries
2024-03-20T21:38:38.713 INFO:tasks.ceph.mgr.x.smithi007.stderr:    if self.mx_last_updated >= ua_last_updated:
2024-03-20T21:38:38.713 INFO:tasks.ceph.mgr.x.smithi007.stderr:AttributeError: 'FSPerfStats' object has no attribute 'mx_last_updated'

This happens because of the new fs creation from qa -> test_dumpfs(). When the stats plugin is enabled and we create a new fs, the fsmap observers are getting notified. Thus FSPerfStats:re_register_queries() is getting called, which was not expected, but self.mx_last_updated was initialised only when 'perf stats' processes an mds report. 

Version-Release number of selected component (if applicable):


How reproducible:
Reproduced by the qa tests.

Steps to Reproduce:
(Look at test_dumpfs(): https://github.com/ceph/ceph/blob/main/qa/tasks/cephfs/test_fstop.py#L93)
1. enable mgr/stats plugin
2. Create a filesystem, mount on 2 clients.
3. Before executing 'perf stats', unmount one client and create a second filesystem. Then mount the second filesytem and continue with `perf stats` querying.
4. AttributeError: 'FSPerfStats' object has no attribute 'mx_last_updated'

Actual results:
The mgr logs shows AttributeError: 'FSPerfStats' object has no attribute 'mx_last_updated'

Expected results:
AttributeError should not appear in the mgr logs.

Additional info: