bssgp_fc_test: do not use real time

Employ osmo_gettimeofday_override_* to take bssgp_fc_test off real time. The
jenkins build slave often failed the test based on sporadic time delays due to
server load and randomly rejected good patches. This patch ends that.

Change-Id: Ie5029b85c2a154554d75d7f9af49a3b93425fdd9
Related: OS#1809
diff --git a/tests/gb/bssgp_fc_test.c b/tests/gb/bssgp_fc_test.c
index d77f141..27d8fcc 100644
--- a/tests/gb/bssgp_fc_test.c
+++ b/tests/gb/bssgp_fc_test.c
@@ -70,6 +70,12 @@
 	struct bssgp_flow_control *fc = talloc_zero(NULL, struct bssgp_flow_control);
 	int i;
 
+	osmo_gettimeofday_override_time = (struct timeval){
+		.tv_sec = 1486385000,
+		.tv_usec = 423423,
+	};
+	osmo_gettimeofday_override = true;
+
 	bssgp_fc_init(fc, bucket_size_max, bucket_leak_rate, max_queue_depth,
 		      fc_out_cb);
 
@@ -83,7 +89,8 @@
 	}
 
 	while (1) {
-		usleep(100000);
+		osmo_gettimeofday_override_add(0, 100000);
+
 		osmo_timers_check();
 		osmo_timers_prepare();
 		osmo_timers_update();