osmo_bsc_main.c: initialize rate counters

main() was missing a call to rate_ctr_init(). Without it, the counters
increased properly, but the times per second / minute / hour etc. values
would always stay at zero.

Change-Id: I4466a7aec51673c79b67614c9dde987633e379e0
Related: OS#3579

src/osmo-bsc/osmo_bsc_main.c

@@ -805,6 +805,7 @@ int main(int argc, char **argv)
 
 	osmo_init_logging2(tall_bsc_ctx, &log_info);
 	osmo_stats_init(tall_bsc_ctx);
+	rate_ctr_init(tall_bsc_ctx);
 
 	/* Allocate global gsm_network struct */
 	rc = bsc_network_alloc();