audit: disable python3 support

audit: disable python3 support

With the version bump to 2.4.3, python3 support was added for
libaudit. With host machines that have python3 installed, this will
cause build issues such as:

  make[5]: Entering directory `/tmp/ryan/buildroot/output/build/audit-2.4.3/bindings/swig/python3'
  swig -o audit_wrap.c -python -py3 -modern -I. -I../../.. -I../../../lib -I/usr/include/python3.4m -I/usr/include/python3.4m ./../src/auditswig.i
  make[5]: swig: Command not found

Solution is to disable python3 support such as we do with python2.7.

Signed-off-by: Ryan Barnett <ryan.barnett@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>