Functional tests for SwiftKerbAuth filter.

This provides an infrastructure for swiftkerbauth
related functional test cases.
More test cases will be added later.
Added a section in swiftkerbauth guide about how to run
functional tests.

test/functional_auth/swiftkerbauth
----------------------------------

A new authentication filter related functional
tests and configuration to reside here.
The configuration would help setup the
environment. All the generic functional tests
should run fine with PASSIVE mode of swiftkerbatuh.
Please refere to swiftkerbatuh documentation for
ACTIVE/PASSIVE mode of working.

swiftkerbauth/test_swkrbath_active.py
-------------------------------------
This file has all the testcases of active mode of
swiftkerbauth. More test cases to be added later.

SwiftKerbAuth related test cases are meant to run
on the setup where SwiftKerbAuth is setup and
installed.

Change-Id: Ibc2a3945f5c9b6714475fcec0ee9d153debb48e3
Signed-off-by: Chetan Risbud <crisbud@redhat.com>
Reviewed-on: http://review.gluster.org/6925
Reviewed-by: Luis Pabon <lpabon@redhat.com>
Tested-by: Luis Pabon <lpabon@redhat.com>