Remove "Switch To Server's Admin" Link for Server Admins

As a follow on to the RFE in Bug #572, I've noticed that the "Switch To Server's Admin" link still shows up in the sidebar (using the Virtualmin Framed Theme) after switching to the server's admin account. Clicking on it again does nothing and may be confusing to server admins. This link should only be displayed for the master system administrator.

Status: 
Closed (fixed)