image with rhel element can't be built if DIB_RHSM_* variables aren't set

[Ivan Berezovskiy]

If you use 'rhel' element for building not-rhel image (CentOS, for example) you shouldn't export parameters like DIB_RHSM_USER, DIB_RHSM_PASSWORD and etc. So, if this parameters are unset, the image build fails with error:

/tmp/in_target.d/pre-install.d/00-rhsm: line 6: DIB_RHSM_USER: unbound variable

Now all scripts have 'set -u', so if any parameter isn't set but it's used in script, then script running fails.

So, I suggest to add line in 'rhel /pre-install.d/00-rhsm' and in 'rhel/finalise.d/60-rhsm-unregister' before 'if' section:

export DIB_RHSM_USER=${DIB_RHSM_USER:-}

If 'DIB_RHSM_USER' will not set, script will not enter in 'if' section because first condition will be false and another variables will not be checked.
It will help to use rhel element with non-rhel images like CentOS.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/93387

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/93387
Committed: https://git.openstack.org/cgit/openstack/diskimage-builder/commit/?id=8995d6402af864a23ee0e50ed7f338395f29d9a4
Submitter: Jenkins
Branch: master

commit 8995d6402af864a23ee0e50ed7f338395f29d9a4
Author: iberezovskiy <email address hidden>
Date: Tue May 13 11:56:53 2014 +0400

    Export unbound variable DIB_RHSM_USER

    If 'DIB_RHSM_USER' isn't set, the image build with rhel
    element fails because of check 'set -u'. So, we should export
    'DIB_RHSM_USER' in script to avoid error during build

    Change-Id: Ic63a20e3d91a25bbe804440a5919b035489c60a3
    Closes-bug: #1318717