So watchdog won't fire for a stalling kit.
After a fork the child has only one thread, but a copy of the watchdog
object.
Stop the watchdog thread before fork, let the child discard its copy of
the watchdog that is now in a discardable state.
And allow it to create a new one on the next SocketPoll ctor.
Signed-off-by: Caolán McNamara <caolan.mcnamara@collabora.com>
Change-Id: I7dc166dca3996401fbdc20cd7643f944662454c8
(cherry picked from commit bb7cd9f357)