mgcp: Allow to dynamically allocate ports from a range..

Allow to switch to a dynamic port allocator and not reuse
the ports for a long time... This should help with a crazy
network sending two streams at the same time.
diff --git a/openbsc/src/mgcp/mgcp_vty.c b/openbsc/src/mgcp/mgcp_vty.c
index d8f6119..f3b5f45 100644
--- a/openbsc/src/mgcp/mgcp_vty.c
+++ b/openbsc/src/mgcp/mgcp_vty.c
@@ -377,6 +377,7 @@
 				LOGP(DMGCP, LOGL_FATAL, "Failed to bind: %d\n", rtp_port);
 				return -1;
 			}
+			endp->bts_end.local_alloc = PORT_ALLOC_STATIC;
 		}
 
 		if (g_cfg->net_ports.mode == PORT_ALLOC_STATIC) {
@@ -386,6 +387,7 @@
 				LOGP(DMGCP, LOGL_FATAL, "Failed to bind: %d\n", rtp_port);
 				return -1;
 			}
+			endp->net_end.local_alloc = PORT_ALLOC_STATIC;
 		}
 	}