add lsm op for getting name of enabled lsm

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
support setting lsm label at exec or immediately

- Add attach test cases

- Moved setting of LSM label later to avoid failure of IPC between parent
  and child during attach

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
use proper config item depending on which lsm is enabled

On a system with AppArmor enabled, if lxc.se_context is configured but
lxc.aa_profile is not (because the user just wants to use the default
AppArmor profile) lxc was passing the lxc.se_context to be set as the
new AppArmor profile. Determine which configuration item to use based
on which lsm is enabled.

Signed-off-by: Dwight Engen <dwight.engen@oracle.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>