This adds unit test for microkernel private pipes.
The code piggybacks to the public pipe test (by
including the same source file), so any updates to
the test will be applied to both.
Note that the prj.mdef are different for both tests, since
the private pipes test move the pipes inside source
code. So, both mdef files will need to be updated at
the same time.
Change-Id: I6fdb5eab7c3a1d6f4b72c26a3620cee0188b07a5
Signed-off-by: Daniel Leung <daniel.leung@intel.com>