identity() took its creation time from process_identity._process_create_time
(psutil only), while identity_is_live judges with update_lock.incarnation_live,
whose producer update_lock.process_create_time falls back to the stdlib probe.
Without psutil every record was written with ct=None, which the reader can only
call unprovable (live), so a killed updater's pause was never orphaned on such a
host. identity() now calls update_lock.process_create_time, the same producer
the marker uses.
Review 5411136378 (#132338) fix 2.
ccca876c94