res_pjsip: delay contact pruning on Asterisk start

Move the call to ast_sip_location_prune_boot_contacts() *after* the call
to ast_res_pjsip_init_options_handling() so that
res/res_pjsip/pjsip_options.c is informed about the contact deletion and
updates its sip_options_contact_statuses list. This allows for an AMI
event to be sent by res/res_pjsip/pjsip_options.c if the endpoint
registers again from the same remote address and port (i.e., same URI)
as used before the Asterisk restart.

ASTERISK-30109
Reported-by: Michael Neuhauser

Change-Id: I1ba4478019e4931a7085f62708d9b66837e901a8