MT#55283 ignore erroneous use of to-tag

The Kamailio control module unconditionally adds the current to-tag to
the control message if rtpp-flags parsing is active. This is generally
not desirable in the case of an initial subscribe-request, as we want a
generated to-tag when the existing to-tag belongs to another dialogue.
Special-case this to ignore the included to-tag if none has been given
explicitly.

Change-Id: I1dc28bfdfd086766e0b6a117c74edd0ebb75d526

daemon/call_interfaces.c

@@ -4201,7 +4201,8 @@ const char *call_subscribe_request_ng(ng_command_ctx_t *ctx) {
 		flags.label = flags.set_label;
 
 	/* get destination monologue */
-	if (!flags.to_tag.len) {
+	// ignore the to-tag if rtpp_flags parsing is active and to-tag wasn't given explicitly
+	if (!flags.to_tag.len || (flags.rtpp_flags && !flags.to_tag_flag)) {
 		/* generate one */
 		flags.to_tag = STR_CONST(rand_buf);
 		rand_hex_str(flags.to_tag.s, flags.to_tag.len / 2);