This reverts commit 3adeb2ab1a.
Commit 3c51d82d0b ("sched/core: Initialize the idle task with preemption
disabled") was reverted because of a bug (b/201047587). Fix is now
available so reintroduces the commit.
Bug: 201047587
Bug: 201771367
Signed-off-by: Woody Lin <woodylin@google.com>
Change-Id: I752da99d92c28a33b8cb2605ff8c2fdf9eb33042