i440fx-test: add test for PAM functionality

This tests PAM settings for the i440fx.  This test does a lot of
byte MMIO which is fairly slow with qtest today.  But the test
does complete in under 2 seconds.

We don't fully emulate PAM largely because of limitations with
KVM so we #if 0 that part of the test case.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Message-id: 1366123521-4330-7-git-send-email-aliguori@us.ibm.com
