Fix socket type to IPv4 in case of no-multi usage

sctp_create_new_listener() takes a parameter server_type which is NOT
the IP version but whether it is an SCTP multihoming server. There was a
bug that when multihoming is not wanted, it created an IPv6 socket
instead of IPv4. This commit fixes this.

IPv6 is not supported yet.

openair3/SCTP/sctp_eNB_task.c

@@ -745,7 +745,7 @@ static int sctp_create_new_listener(
     }
   }
   else {
-    if ((sd = socket(AF_INET6, SOCK_STREAM, IPPROTO_SCTP)) < 0) {
+    if ((sd = socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP)) < 0) {
       SCTP_ERROR("socket: %s:%d\n", strerror(errno), errno);
       return -1;
     }