Remove a few more stray __FBSDID uses

Reviewed by: imp, emaste
Differential Revision: https://reviews.freebsd.org/D41954

jail: allow root to implicitly widen its cpuset to attach

The default behavior for attaching processes to jails is that the jail's
cpuset augments the attaching processes, so that it cannot be used to
escalate a user's ability to take advantage of more CPUs than the
administrator wanted them to.

This is problematic when root needs to manage jails that have disjoint
sets with whatever process is attaching, as this would otherwise result
in a deadlock. Therefore, if we did not have an appropriate common
subset of cpus/domains for our new policy, we now allow the process to
simply take on the jail set *if* it has the privilege to widen its mask
anyways.

With the new logic, root can still usefully cpuset a process that
attaches to a jail with the desire of maintaining the set it was given
pre-attachment while still retaining the ability to manage child jails
without jumping through hoops.

A test has been added to demonstrate the issue; cpuset of a process
down to just the first CPU and attempting to attach to a jail without
access to any of the same CPUs previously resulted in EDEADLK and now
results in taking on the jail's mask for privileged users.

PR: 253724
Reviewed by: jamie (also discussed with)
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D28952

libc: tests: add some tests for cpuset(2)

The cpuset(2) tests should be run as root (require.user properly set) with
>= 3 cpus for maximum coverage. All tests that want to modify the cpuset
don't assume any particular cpu layout (i.e. the first cpu may not be 0, the
last may not be first + count) and the following scenarios are tested:

1.) newset: basic execute cpuset() to grab a new cpuset, make sure the
assigned cpuset then has a different ID.
2.) transient: create a new cpuset then assign the process its original
cpuset, ensuring that the one we created is now gone.
3.) deadlk: test assigning an anonymous mask, then resetting the process
base affinity with 1-cpu overlap w.r.t. the anonymous mask and with
0-cpu overlap w.r.t. the anonymous mask.
4.) jail_attach_newbase: process attaches to a jail with its own
cpuset+mask (e.g. cpuset -c -l 1,2 jail -c path=/ command=/bin/sh)
5.) jail_attach_newbase_plain: process attaches to a jail with its own
cpuset (e.g. cpuset -c jail -c path=/ command=/bin/sh)
6.) jail_attach_prevbase: process attaches to a jail with the containing
jail's root cpuset (e.g. jail -c path=/ command=/bin/sh)
7.) jail_attach_plain: process attaches to a jail with the containing jail's
root cpuset+mask.
8.) badparent: creates a new cpuset and modifies the anonymous thread mask,
then setid's back to the original and checks that cpuset_getid() returns
the expected set.

Differential Revision: https://reviews.freebsd.org/D27307