res_pjsip: Fix prune_on_boot to remove only contacts for the host.

* Check that the contact's reg_server matches the host's name before
deleting any prune_on_boot contacts.  We don't want to delete reliable
transport contacts made with other servers if the ps_contacts database
table is shared with other servers.

Thanks to Ross Beer for pointing out that the original prune logic would
delete reliable transport contacts from other servers.

ASTERISK-27147

Change-Id: I8e439d0d1c266ffdfd7b73d1e5e466180a689bd0

res/res_pjsip/location.c

@@ -467,7 +467,10 @@ static int prune_boot_contacts_cb(void *obj, void *arg, int flags)
 {
 	struct ast_sip_contact *contact = obj;
 
-	if (contact->prune_on_boot) {
+	if (contact->prune_on_boot
+		&& !strcmp(contact->reg_server, ast_config_AST_SYSTEM_NAME ?: "")) {
+		ast_verb(3, "Removed contact '%s' from AOR '%s' due to system boot\n",
+			contact->uri, contact->aor);
 		ast_sip_location_delete_contact(contact);
 	}