50-heat-config-docker-cmd error for empty config

[Steve Baker]

When there are no docker-cmd configs the following error is raised. The error is harmless but misleading, so empty config should be properly handled.

dib-run-parts Wed Dec 7 23:02:48 UTC 2016 Running /usr/libexec/os-refresh-config/configure.d/50-heat-config-docker-cmd
Traceback (most recent call last):
  File "/usr/libexec/os-refresh-config/configure.d/50-heat-config-docker-cmd", line 144, in <module>
    sys.exit(main(sys.argv))
  File "/usr/libexec/os-refresh-config/configure.d/50-heat-config-docker-cmd", line 59, in main
    cmd_configs = list(build_configs(configs))
UnboundLocalError: local variable 'configs' referenced before assignment

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/408347

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/408347
Committed: https://git.openstack.org/cgit/openstack/heat-templates/commit/?id=d10069ac13897bea8f2e296070081b74cf927e05
Submitter: Jenkins
Branch: master

commit d10069ac13897bea8f2e296070081b74cf927e05
Author: Steve Baker <email address hidden>
Date: Thu Dec 8 12:25:06 2016 +1300

    docker-cmd hook handle empty config file

    Early in a server boot the file /var/run/heat-config/heat-config may
    exist but be empty. This causes a stack trace to be raised in this
    script.

    This change detects a json parse error and exits gracefully.

    Change-Id: I29d731098659bfbf10a2caf80c2cfc49de5df4cc
    Closes-Bug: #1648249