Introduce an apparmor.aa.init_aa() method and move the initialization
code of the apparmor.aa module into it. Note that this change will break
any external users of apparmor.aa because global variables that were
previously initialized when importing apparmor.aa will not be
initialized unless a call to the new apparmor.aa.init_aa() method is
made.

The main purpose of this change is to allow the utils tests to be able
to set a non-default location for configuration files. Instead of
hard-coding the location of logprof.conf and other utils related
configuration files to /etc/apparmor/, this patch allows it to be
configured by calling apparmor.aa.init_aa(confdir=PATH).

This allows for the make check target to use the in-tree config file,
profiles, and parser by default. A helper method, setup_aa(), is added
to common_test.py that checks for an environment variable containing a
non-default configuration directory path prior to calling
apparmor.aa.init_aa(). All test scripts that use apparmor.aa are updated
to call setup_aa().

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Suggested-by: Christian Boltz <apparmor@cboltz.de>
Acked-by: Seth Arnold <seth.arnold@canonical.com>
Acked-by: Christian Boltz <apparmor@cboltz.de>