We're seeing failures where the UI hangs if the server disappears. Ping
the cooker/server if we've not had any events in the last minute so we can
check if it is still alive.
(Bitbake rev: 6567ad6181f9e39812097f0154647e4b38238fdd)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>