pulse-server: leave the draining state

Use pw_stream_set_active() to leave the draining state so that our
process methods are called again and we can resume.

src/modules/module-protocol-pulse/pulse-server.c

@@ -1306,6 +1306,8 @@ static void stream_drained(void *data)
 				stream->drain_tag);
 		reply_simple_ack(stream->client, stream->drain_tag);
 		stream->drain_tag = 0;
+
+		pw_stream_set_active(stream->stream, true);
 	}
 }