qa: Fix test_cephfs_mirror_restart_sync_on_blocklist

qa: Fix test_cephfs_mirror_restart_sync_on_blocklist

With the new retry logic introduced in PR 7305, the sleep
was removed. However, the retry mechanism currently
triggers only for AssertionError, KeyError, and IndexError.

The command can also fail with CommandFailedError, as
observed in the blocklist test case. In this scenario,
FSMirror initialization has not yet started, but the
command is still issued, leading to failure.

Therefore, add CommandFailedError to the list of
retryable exceptions.

Fixes: https://tracker.ceph.com/issues/74998
Signed-off-by: Kotresh HR <khiremat@redhat.com>