cm_ncd_callback re-entered cm_start_phase_reverse on every NCD timeout
during REVERSE phase (shared NCD revived by other modules), leaking reverse
timers: only the last one was tracked in entry->main.timer, so cm_entry_cleanup
cancelled only that one and the earlier timers fired on the freed entry.
- ignore repeated NCD timeouts while already in REVERSE (phase==2)
- cancel entry->main.timer before overwriting in reverse/indirect phases
- remove entry from reverse_pending in cm_entry_cleanup
evgeny
ee54bd52b3