Gem5Device: Addressed review comments
Gem5Device: Addressed review comments

- Replaced hard-coded pexpect expect string with UNIQUE_PROMPT.

- Changed the capture_screen debug to a warning to make sure that the
  user knows when it happens.

- Fixed the logic for checking when a file exists. Previously, if the
  output could not correctly be processed (ValueError) then we just
  assumed that the file existed if there was any output at all. This
  is clearly not a good default. Changed to default to False if it was
  not able to process the output as this seems to be the safest
  option.

- Changed ad hoc filename extraction to use os.path.basename.

- Removed the processing of some kwargs and defaults that are handled
  by the parent class.

- Stopped overriding some paramaters which were purely defined in the
  Gem5Device.

lisatn/workload-automation,bjackman/workload-automation,muendelezaji/workload-automation,jimboatarm/workload-automation,lisatn/workload-automation,Sticklyman1936/workload-automation,muendelezaji/workload-automation,ARM-software/workload-automation,ARM-software/workload-automation,bjackman/workload-automation,setrofim/workload-automation,bathepawan/workload-automation,chase-qi/workload-automation,ep1cman/workload-automation,bathepawan/workload-automation,muendelezaji/workload-automation,chase-qi/workload-automation,bathepawan/workload-automation,jimboatarm/workload-automation,jimboatarm/workload-automation,Sticklyman1936/workload-automation,bjackman/workload-automation,Sticklyman1936/workload-automation,ep1cman/workload-automation,setrofim/workload-automation,ARM-software/workload-automation,setrofim/workload-automation,bathepawan/workload-automation,ep1cman/workload-automation,ep1cman/workload-automation,ARM-software/workload-automation,bathepawan/workload-automation,setrofim/workload-automation,Sticklyman1936/workload-automation,muendelezaji/workload-automation,jimboatarm/workload-automation,chase-qi/workload-automation,Sticklyman1936/workload-automation,chase-qi/workload-automation,lisatn/workload-automation,jimboatarm/workload-automation,bjackman/workload-automation,Sticklyman1936/workload-automation,ep1cman/workload-automation,ep1cman/workload-automation,bjackman/workload-automation,bjackman/workload-automation,lisatn/workload-automation,muendelezaji/workload-automation,chase-qi/workload-automation,bathepawan/workload-automation,chase-qi/workload-automation,muendelezaji/workload-automation,jimboatarm/workload-automation