Add VTY command to specify default speech codec

In order to have the MNCC application reliably decide on the codec type,
it needs to know if we are running on a TCH/F or TCH/H.  Thus, we pass
lchan_mode as a new parameter to the 'struct gsm_mncc'
diff --git a/openbsc/src/libcommon/common_vty.c b/openbsc/src/libcommon/common_vty.c
index 5b4b296..e8486f4 100644
--- a/openbsc/src/libcommon/common_vty.c
+++ b/openbsc/src/libcommon/common_vty.c
@@ -86,12 +86,11 @@
 	case PGROUP_NODE:
 		vty->node = NAT_NODE;
 		break;
-	case MSC_NODE:
-		vty->node = CONFIG_NODE;
-		break;
 	case TRUNK_NODE:
 		vty->node = MGCP_NODE;
 		break;
+	case MSC_NODE:
+	case MNCC_INT_NODE:
 	default:
 		vty->node = CONFIG_NODE;
 	}
@@ -161,6 +160,7 @@
 		vty->index = NULL;
 		break;
 	case MSC_NODE:
+	case MNCC_INT_NODE:
 		vty->node = CONFIG_NODE;
 		break;
 	case TRUNK_NODE:
@@ -197,6 +197,7 @@
 	case NAT_BSC_NODE:
 	case PGROUP_NODE:
 	case MSC_NODE:
+	case MNCC_INT_NODE:
 		vty_config_unlock(vty);
 		vty->node = ENABLE_NODE;
 		vty->index = NULL;