Could not open Management UI after global setting change.

[Dan Dong]

Hi, Experts,
  When I modified the global settings for "secstorage.allowed.internal.sites"
to a different network parameter, I found I could not open the
http://localhost:8080/client UI page anymore, so I could not change back to
the original setting again. How to solve this? Where can I find the
configuration file path on the Management Ububtu server so I can modify it
back by hand? Thanks!

Cheers,
Dan