lsm: borrow lsm from LXC

Signed-off-by: Andrey Vagin <avagin@openvz.org>
process: add ability to set a security label (v3)

v2: don't change a security label, if it isn't set.
v3: handle lsm_label in local_desc_copy()

Signed-off-by: Andrey Vagin <avagin@openvz.org>
test: add list of tests, which should be executed for all drivers

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