wireguard: park the timer process

wireguard: park the timer process

Until the feature is configured. It would make sense to push more of
the feature init code into the newly-added wg_feature_init()
function. This patch fixes a severe hemorrhoid.

Type: improvement

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I87095575363baa41407dd52492159a7b8c2899e7