res_pjsip: Prevent SEGV in pjsip_evsub_send_request

res_pjsip: Prevent SEGV in pjsip_evsub_send_request

contributed pjproject - patch to check sub->pending_notify
in evsub.c:on_tsx_state before calling
pjsip_evsub_send_request()

res_pjsip_pubsub - change post pjsip 2.13 behavior to use
pubsub_on_refresh_timeout to avoid the ao2_cleanup call on
the sub_tree. This is is because the final NOTIFY send is no
longer the last place the sub_tree is referenced.

ASTERISK-30419

Change-Id: Ib5cc662ce578e9adcda312e16c58a10b6453e438