security: apparmor: Properly link with storage driver in helper program

security: apparmor: Properly link with storage driver in helper program

The refactor to split up storage driver into modules broke the apparmor
helper program, since that did not initialize the storage driver
properly and thus detection of the backing chain could not work.

Register the storage driver backends explicitly. Unfortunately it's now
necessary to link with the full storage driver to satisfy dependencies
of the loadable modules.

Reviewed-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Reported-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
Tested-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>