Scheduler updates for 9.4

JIRA: https://issues.redhat.com/browse/RHEL-1536
Depends: https://bugzilla.redhat.com/show_bug.cgi?id=2208016

Tested: With scheduelr stress tests, cfs bandwidth tests and unit tests on
specific pieces (such as enabling WARN_DOUBLE_CLOCK etc), in addition to cki
and perf QE testing.

Updates and fixes from up to v6.5 for scheduler related code. This includes
a revert of one of the RT merge patches which is then re-applied in the form
it took when added to Linus's tree (see the "wait_task_inactive()" commits).

Signed-off-by: Phil Auld pauld@redhat.com