zdtm: add a new test case, which generate a random process tree
zdtm: wait all children during cleaning up
restore: add a synchronisation point after restoring credential

For security reason processes can be resumed only when all
credentials are restored. Otherwise someone can attach to a
process, which are not restored credentials yet and execute
some code.
restore: handle errors of setting credentials
zdtm: execite test cases from a test user

Signed-off-by: Andrew Vagin <avagin@openvz.org>
socket-ext: provide access to socket for a test user
Revert "make: Don't generate tags/cscope for tools/ and test/"

This reverts commit 396a08eb95133ab61eedce6cc3cd960d27f7efeb.
zdtm: check bset in caps00