This is intended for testing USB event delivery to TSR plugins.
Usage:
1. enter plugin -> select Start
2. plug and unplug USB
3. reenter plugin -> select Status
it should display "State: disconnected" then "Prev: connected"
4. when done -> select Stop Plugin
Change-Id: I6c70f452db642f3fcbfbcb4f06c57f93e60f4cfd
