cephfs_mirror: check if init in progress before calling FSMirror::is_…

…failed()

Fixes the crash:
```
std::scoped_lock<std::mutex>::scoped_lock (__m=..., this=<optimized out>, this=<optimized out>, __m=...) at /usr/include/c++/11/mutex:655
cephfs::mirror::MirrorWatcher::is_failed (this=0x0) at /usr/src/debug/ceph-19.0.0-1578.g3d482f42.el9.x86_64/src/tools/cephfs_mirror/MirrorWatcher.h:56
cephfs::mirror::FSMirror::is_failed (this=0x557478284340) at /usr/src/debug/ceph-19.0.0-1578.g3d482f42.el9.x86_64/src/tools/cephfs_mirror/FSMirror.h:52
cephfs::mirror::Mirror::update_fs_mirrors (this=0x5574773c3e60) at /usr/src/debug/ceph-19.0.0-1578.g3d482f42.el9.x86_64/src/tools/cephfs_mirror/Mirror.cc:515

```

Fixes: https://tracker.ceph.com/issues/64751
Signed-off-by: Jos Collin <jcollin@redhat.com>

src/tools/cephfs_mirror/Mirror.cc

@@ -556,7 +556,8 @@ void Mirror::update_fs_mirrors() {
   {
     std::scoped_lock locker(m_lock);
     for (auto &[filesystem, mirror_action] : m_mirror_actions) {
-      auto failed_restart = mirror_action.fs_mirror && mirror_action.fs_mirror->is_failed() &&
+      bool failed = mirror_action.fs_mirror->m_on_init_finish == nullptr)? mirror_action.fs_mirror->is_failed(): false;
+      auto failed_restart = mirror_action.fs_mirror && failed &&
 	(failed_interval > 0 && (mirror_action.fs_mirror->get_failed_ts() - now) > failed_interval);
       auto blocklisted_restart = mirror_action.fs_mirror && mirror_action.fs_mirror->is_blocklisted() &&
 	(blocklist_interval > 0 && (mirror_action.fs_mirror->get_blocklisted_ts() - now) > blocklist_interval);