apparmor: docker-default: Include base abstraction

Encountered problems on 14.04 relating to signals between container
processes being blocked by apparmor. The base abstraction contains
appropriate rules to allow this communication.

Docker-DCO-1.1-Signed-off-by: Michael Brown <michael.brown@discourse.org> (github: Supermathie)
apparmor: abstractions/base expects pid variable

Add 'pid' variable pointing to 'self' to allow parsing of profile to succeed

Docker-DCO-1.1-Signed-off-by: Michael Brown <michael.brown@discourse.org> (github: Supermathie)
apparmor: pull in variables from tunables/global

The variables that were defined at the top of the apparmor profile are best
pulled in via the <tunables/global> include.

Docker-DCO-1.1-Signed-off-by: Michael Brown <michael.brown@discourse.org> (github: Supermathie)
Merge pull request #5049 from Supermathie/aa-fix

apparmor: docker-default: Include base abstraction