gprs_ns: Set sockaddr_in.sin_family for persistent NSVCs

We cannot just set sockaddr_in.sin_addr + sin_port, we also must
initializa sin_family.  The reason this has worked so far is
because we probably always first received a NS packet from the
peer, rather than being the first one to send.

Change-Id: I6cefc2cd5516c7a4c01a2cc040afca454e59dd57
Related: OS#4629
diff --git a/src/gb/gprs_ns_vty.c b/src/gb/gprs_ns_vty.c
index 38d4393..a39e139 100644
--- a/src/gb/gprs_ns_vty.c
+++ b/src/gb/gprs_ns_vty.c
@@ -318,6 +318,7 @@
 		vty_out(vty, "No such NSE (%u)%s", nsei, VTY_NEWLINE);
 		return CMD_WARNING;
 	}
+	nsvc->ip.bts_addr.sin_family = AF_INET;
 	inet_aton(argv[1], &nsvc->ip.bts_addr.sin_addr);
 
 	return CMD_SUCCESS;