Admin Server crashes when retrieving metrics

[andrewjstone]

The cli command metrics <Pid> causes the admin server to crash: ajs@shelbs:~/haret$ thread '<unnamed>' panicked at 'internal error: entered unreachable code', haret/src/admin/connection_handler.rs:93

Oddly enough this only brings down that thread. The rest of the system, including clients continues to work. That seems to be an error in the thread join code that also could use fixing.