Fix broken ctrl commands

Recent changes to libosmoctrl resulted in ctrl comands being broken
because local lookup helper returned incorrect value for ROOT_NODE.

Note: although this commit seems to fix it for me, I'm still not sure
how the logic behind lookup function return values work. Would be nice
to get it documented.

Change-Id: Iddd20602047ebd9be1b668593f5dfa6f1d3e8369
diff --git a/src/ctrl/fsm_ctrl_commands.c b/src/ctrl/fsm_ctrl_commands.c
index 0dfc396..64324f2 100644
--- a/src/ctrl/fsm_ctrl_commands.c
+++ b/src/ctrl/fsm_ctrl_commands.c
@@ -33,7 +33,8 @@
 				goto err_missing;
 			*node_data = fsm;
 			*node_type = CTRL_NODE_FSM;
-		}
+		} else
+			return 0;
 		break;
 	case CTRL_NODE_FSM:
 		fsm = *node_data;