src/test/reclaim: test session reclaim after mds failover

ensure that the new active MDS reads the auth_name from the ESession
event and assigns it to the new session that MDS creates during journal
replay.

NOTE: the mds failover is carried by sending "respawn" command to active
MDS using libcephfs's ceph_mds_command().

Fixes: https://tracker.ceph.com/issues/76728
Signed-off-by: Dhairya Parmar <dparmar@redhat.com>