mgcp_vty: fix config write for trunk 0

When a trunk 0 is created (which is legal) than it is impossible to
write this trunk back to the config. The reason for this that there is
still a filtering in place from the time where trunk 0 was not allowed.
This filter needs to be extended to filter only virtual trunk 0 but not
E1 trunk 0 out.

Change-Id: Iad6b577b5a711c35f98c477351fde567d8c87298
diff --git a/src/libosmo-mgcp/mgcp_vty.c b/src/libosmo-mgcp/mgcp_vty.c
index 74e8da0..681ca99 100644
--- a/src/libosmo-mgcp/mgcp_vty.c
+++ b/src/libosmo-mgcp/mgcp_vty.c
@@ -958,7 +958,8 @@
 		   config of trunk 0 here. The configuration for the virtual
 		   trunk is written by config_write_mgcp(). */
 
-		if (trunk->trunk_nr == MGCP_VIRT_TRUNK_ID)
+		if (trunk->trunk_type == MGCP_TRUNK_VIRTUAL
+		    && trunk->trunk_nr == MGCP_VIRT_TRUNK_ID)
 			continue;
 
 		vty_out(vty, " trunk %d%s", trunk->trunk_nr, VTY_NEWLINE);