ceph: add manual reset debugfs control and tracepoints

ceph: add manual reset debugfs control and tracepoints

Add the debugfs and trace plumbing used to trigger and observe
manual client reset.

The reset interface exposes a trigger file for operator-initiated
reset and a status file for tracking the most recent run.  The
tracepoints record scheduling, completion, and blocked caller
behavior so reset progress can be diagnosed from the client side.

debugfs layout under /sys/kernel/debug/ceph/<client>/reset/:
  trigger - write to initiate a manual reset
  status  - read to see the most recent reset result

The reset directory is cleaned up via debugfs_remove_recursive()
on the parent, so individual file dentries are not stored.

Tracepoints:
  ceph_client_reset_schedule  - reset queued
  ceph_client_reset_complete  - reset finished (success or failure)
  ceph_client_reset_blocked   - caller blocked waiting for reset
  ceph_client_reset_unblocked - caller unblocked after reset

All tracepoints use a null-safe access for monc.auth->global_id
to guard against early-init or late-teardown edge cases.

Signed-off-by: Alex Markuze <amarkuze@redhat.com>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>