[uac_registrant] fix passing wrong context to authenticated REGISTER

When sending the authenticating REGISTER, be sure a new context is provided. This will avoid the usage of the context belonging to the first (challenged) REGISTER. This mixup of the context was breaking the tracing of these REGISTER requests via local route.

(cherry picked from commit c64766a)

modules/uac_registrant/registrant.c

@@ -765,6 +765,7 @@ int send_register(unsigned int hash_index, reg_record_t *rec, str *auth_hdr)
 {
 	int result, expires_len;
 	reg_tm_cb_t *cb_param;
+	context_p old_ctx;
 	char *p, *expires;
 
 	/* Allocate space for tm callback params */
@@ -811,14 +812,32 @@ int send_register(unsigned int hash_index, reg_record_t *rec, str *auth_hdr)
 	LM_DBG("extra_hdrs=[%p][%d]->[%.*s]\n",
 		extra_hdrs.s, extra_hdrs.len, extra_hdrs.len, extra_hdrs.s);
 
-	result=tmb.t_request_within(
-		&register_method,	/* method */
-		&extra_hdrs,		/* extra headers*/
-		NULL,			/* body */
-		&rec->td,		/* dialog structure*/
-		reg_tm_cback,		/* callback function */
-		(void *)cb_param,	/* callback param */
-		osips_shm_free);	/* function to release the parameter */
+	old_ctx = current_processing_ctx;
+	if ( (current_processing_ctx = context_alloc(CONTEXT_GLOBAL))==NULL ) {
+
+		LM_ERR("failed to alloc new ctx in pkg\n");
+		result = 0;
+
+	} else {
+
+		/* reset the new to-be-used CTX */
+		memset( current_processing_ctx, 0, context_size(CONTEXT_GLOBAL) );
+
+		/* send the request within the new context */
+		result=tmb.t_request_within(
+			&register_method,	/* method */
+			&extra_hdrs,		/* extra headers*/
+			NULL,			/* body */
+			&rec->td,		/* dialog structure*/
+			reg_tm_cback,		/* callback function */
+			(void *)cb_param,	/* callback param */
+			osips_shm_free);	/* function to release the parameter */
+
+		clear_global_context();
+
+	}
+
+	current_processing_ctx = old_ctx;  /* restore prev context */
 
 	if (result < 1)
 		shm_free(cb_param);