Revert "cgroup: refactor allow_attach function into common code"

This reverts commit 16474253.

Part of Chromium commit series:

CHROMIUM: remove Android's cgroup generic permissions checks

The implementation is utterly broken, resulting in all processes being
allows to move tasks between sets (as long as they have access to the
"tasks" attribute), and upstream is heading towards checking only
capability anyway, so let's get rid of this code.

BUG=b:31790445,chromium:647994
TEST=Boot android container, examine logcat

Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/394967


Reviewed-by: Ricky Zhou <rickyz@chromium.org>
Reviewed-by: John Stultz <john.stultz@linaro.org>

Change-Id: I7d64a291ae1347281632b7cb82110f858fefeace
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>