Plug another leak.

If cf_export_specified_packets() succeeds, and it wrote to a temporary
file, it leaks the name of the file to which it was writing.  Free that
after we've renamed that file on top of the target file (safe save).


(cherry picked from commit 8ca86b29bf)

file.c

@@ -4907,6 +4907,7 @@ cf_export_specified_packets(capture_file *cf, const char *fname,
       cf_rename_failure_alert_box(fname, errno);
       goto fail;
     }
+    g_free(fname_new);
   }
 
   return CF_WRITE_OK;