baseline fails on detached head state

[Stanislaw Pitucha]

Job http://logs.openstack.org/59/263059/1/check/gate-bandit-linters/e2a4714/console.html shows the issue: (slightly redacted)

+ timeout -s SIGINT 0 git fetch http://zm04.openstack.org/p/openstack/bandit refs/zuul/master/Zf5634ebf3b0f4c0785fb862780f66be5
+ git checkout FETCH_HEAD
+ git reset --hard FETCH_HEAD
+ git clean -x -f -d -q
/home/jenkins/workspace/gate-bandit-linters$ /home/jenkins/workspace/gate-bandit-linters/.tox/linters/bin/bandit-baseline -r bandit -ll -ii
Traceback (most recent call last):
  File ".tox/linters/bin/bandit-baseline", line 11, in <module>
    sys.exit(main())
  File "/home/jenkins/workspace/gate-bandit-linters/.tox/linters/local/lib/python2.7/site-packages/bandit/bandit_baseline.py", line 66, in main
    branch = repo.active_branch
  File "/home/jenkins/workspace/gate-bandit-linters/.tox/linters/local/lib/python2.7/site-packages/git/repo/base.py", line 631, in active_branch
    return self.head.reference
  File "/home/jenkins/workspace/gate-bandit-linters/.tox/linters/local/lib/python2.7/site-packages/git/refs/symbolic.py", line 258, in _get_reference
    raise TypeError("%s is a detached symbolic reference as it points to %r" % (self, sha))
TypeError: HEAD is a detached symbolic reference as it points to '3dae02fd6d83105c139d07b3f6bf294b98986dea'

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/263072

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/263072
Committed: https://git.openstack.org/cgit/openstack/bandit/commit/?id=32c5921185a31735dc715ed352c0980b6b3d1739
Submitter: Jenkins
Branch: master

commit 32c5921185a31735dc715ed352c0980b6b3d1739
Author: Stanisław Pitucha <email address hidden>
Date: Mon Jan 4 10:59:35 2016 +1100

    Fix detached head baseline

    Closes-bug: 1530722
    Change-Id: I75f74ef78807c54a0e26c2d77b99992defb523c7