lxd: Provide apparmor_parser

Previously, lxd would complain about apparmor_parser being missing:

lxd[1037]: lvl=warn msg="AppArmor support has been disabled because 'apparmor_parser' couldn't be found" t=2018-11-19T18:32:47-0800

We need to provide a wrapped apparmor_parser that knows where to find
<tunables/global>, which is #included by lxd’s generated profiles.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>