build-stx-images.sh fails to build docker images

[Don Penney]

Brief Description
-----------------
When attempting to build an image with BUILDER=docker, build-stx-images.sh fails with:
get_git '' ''
basename: missing operand
Try 'basename --help' for more information.
git repo appears to be invalid: . Aborting...
Failed to clone or update . Aborting...

Severity
--------
Critical

Reproducibility
---------------
Reproducible

System Configuration
--------------------
Build system

Branch/Pull Time/Commit
-----------------------
Bug introduced by:
https://review.opendev.org/661811

Test Activity
-------------
Developer Testing

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/662228
Committed: https://git.openstack.org/cgit/starlingx/root/commit/?id=8f42b58cf355288fbb01fea8bec6f0137be0bb44
Submitter: Zuul
Branch: master

commit 8f42b58cf355288fbb01fea8bec6f0137be0bb44
Author: Don Penney <email address hidden>
Date: Thu May 30 09:58:22 2019 -0400

    Image builds broken for BUILDER=docker

    A recent update to build-stx-images.sh broke the building
    of images with BUILDER=docker. A bash syntax error was
    introduced that leads to invalid function calls, resulting
    in the following error:

        get_git '' ''
        basename: missing operand
        Try 'basename --help' for more information.
        git repo appears to be invalid: . Aborting...
        Failed to clone or update . Aborting...

    This update corrects the bash syntax.

    Change-Id: I09487869350af82b13d9670ff7035078c4a21d4a
    Closes-Bug: 1831093
    Signed-off-by: Don Penney <email address hidden>

[Ghada Khalil (gkhalil)]

Marking as release gating; build system issue