Don't override the defaults unless required.

This patch adds S_IRUSR as the third parameter to open()
in the DFLP locking unit test.

The LITMUS^RT kernel was changed to no longer test for "invalid" CPU
paramters to allow reuse of the CPU parameter to denote virtual CPUs,
reservations, etc.

This patch removes the corresponding test.

This crashes old versions of the kernel. Kernel patches fixing the
various panics have been merged into the kernel staging tree.

Complements the prior test for suspended tasks. All plugins currently
pass this test.

The kernel needs to be able to deal with tasks that do not make
themselves a real-time task, but get configured by some other task
instead.

The sproadic_*() macros have become unwieldy. This patch
replaces those convenience macros for global, clustered,
and partitioned scheduling. A part of this API change
is the explicit use of nanosecond time-values. Prior APIs
have used lt_t (litmus time), which had an implied time
scale of nanoseconds.

/bin apps and test suite also updated to use revised API.
Modifications to the test suite are mostly centered around
using nanoseconds instead of milliseconds.