Wip/martyn/t7336 speed up ubihealthd shutdown

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>

The ubihealthd utility has been found to take a long time to shutdown when
requested. A patch has been identified on the mailing list that rectifies
this issue. Add a slightly modified version fo that patch.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>