[RHEL8][CONTAINER] Runtime check when creating pThreads

@raymond.knopp @florian.kaltenberger @hardy @ismail

It looks like :

• when running on a Fedora-host
• with generic kernel
• in a container
• even in privileged mode

That is not enough and priority/schedule settings is not allowed.

So at runtime, we check and in case, we don't set up priorities.