MFC r274583: Default to use 10 seconds as nap interval instead of 1.

MFC r308040,308479: nap time between pats is forced to be at most half
of the timeout

Note that in this branch the default nap period is 1 second unlike
the head where the period is 10 seconds.

Revert r308753: some unrelated changes were included into the commit

MFC r308040,308479: nap time between pats is forced to be at most half
of the timeout

Note that in this branch the default nap period is 1 second unlike the
head where the period is 10 seconds.

MFC r286947: Add a new exit-timeout option to watchdogd.

MFC r286947: Add a new exit-timeout option to watchdogd.