zdtm: add new test case for "pipe inversion"

Probably all of you know about "lock inversion". We have a similar
problem on restoring pipes.

This test case creates two process and two pipes.
process 1:
	11: pipe1 (w)
	12: pipe2 (r)
process 2:
	11: pipe2 (r)
	12: pipe1 (w)

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>