pulse: fix discovery of newly added devices

Fix regression introduced in 7bc5e28d
preventing the device provider to send the device-added message for new
devices.
By early returning the patch was discarding add/remove events.

Fix #735

Part-of: <gstreamer/gst-plugins-good!626>

ext/pulse/pulsedeviceprovider.c

@@ -341,8 +341,6 @@ context_subscribe_cb (pa_context * context, pa_subscription_event_type_t type,
   if (facility == PA_SUBSCRIPTION_EVENT_SERVER ||
       facility != PA_SUBSCRIPTION_EVENT_CHANGE) {
     pa_context_get_server_info (self->context, get_server_info_cb, self);
-
-    return;
   }
 
   if (facility != PA_SUBSCRIPTION_EVENT_SOURCE &&