Fix tunable and sysctl handling of the fail_on_task_timeout knob.

Reviewed by:	emax
Obtained from:	Netflix, Inc.
MFC after:	3 days


git-svn-id: svn+ssh://svn.freebsd.org/base/head@276174 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f