Release master before shutting down on a terminal on child_exit

If the shell running in a console terminates, frecon shuts down
the terminal and starts a new one.  However, if it holds onto
master during that process, then the init of the new terminal
can sometimes fail.

BUG=chromium:443853
TEST=use ctrl-d on console on link_freon while:
  (a) everything idle
  (b) playing video in a window
  (c) playing full-screen video

Change-Id: I9420cf063d354d33c3fcb434e4f9d12e90d84022
Reviewed-on: https://chromium-review.googlesource.com/236922
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Commit-Queue: David Sodman <dsodman@chromium.org>
Tested-by: David Sodman <dsodman@chromium.org>
Trybot-Ready: David Sodman <dsodman@chromium.org>
2 files changed