extcap: Fix a memory leak

Change-Id: I3a7e5d10d0007972c18ccbb49f40114c700a88e2
Reviewed-on: https://code.wireshark.org/review/36822
Petri-Dish: Stig Bjørlykke <stig@bjorlykke.org>
Tested-by: Petri Dish Buildbot
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>

extcap_parser.c

@@ -245,6 +245,7 @@ static void extcap_free_value(extcap_value *v) {
 
     g_free(v->call);
     g_free(v->display);
+    g_free(v->parent);
 
     g_free(v);
 }