nitb/ctrl: Add command to add/modify a subscriber to the database

The test has been manually verified. Executing the select for
the subscribers showed:

sqlite> select * from Subscriber;
1|2014-03-23 12:12:46|2014-03-23 12:19:09|2620345||445567|1||0|

This created a subscriber with the right IMSI, MSISDN and has
it authorized.

Fixes: SYS#275
diff --git a/openbsc/src/osmo-nitb/bsc_hack.c b/openbsc/src/osmo-nitb/bsc_hack.c
index 67c65ce..c78e3ec 100644
--- a/openbsc/src/osmo-nitb/bsc_hack.c
+++ b/openbsc/src/osmo-nitb/bsc_hack.c
@@ -291,7 +291,12 @@
 	}
 
 	if (bsc_base_ctrl_cmds_install() != 0) {
-		printf("Failed to initialize the control commands. Exiting.\n");
+		printf("Failed to initialize the BSC control commands.\n");
+		return -1;
+	}
+
+	if (msc_ctrl_cmds_install() != 0) {
+		printf("Failed to initialize the MSC control commands.\n");
 		return -1;
 	}