sip: Start the application even if sofia-sip is broken

In case of solely managing the application through the VTY we
want/need to have the application running besides a wrong config
has been entered. SIP will be broken but a user will be able to
see the log message and can fix it.

src/main.c

@@ -148,10 +148,9 @@ int main(int argc, char **argv)
 	/* sofia sip */
 	sip_agent_init(&g_app.sip.agent, &g_app);
 	rc = sip_agent_start(&g_app.sip.agent);
-	if (rc < 0) {
-		LOGP(DSIP, LOGL_ERROR, "Failed to initialize SIP.\n");
-		exit(1);
-	}
+	if (rc < 0)
+		LOGP(DSIP, LOGL_ERROR,
+			"Failed to initialize SIP. Running broken\n");
 
 	calls_init();
 	app_setup(&g_app);