Update py-google-compute-engine to 20170829.

August 29, 2017

  * New packaging for Debian, CentOS, and RHEL.
  * Fix for updating EL 6 package in the SCL Python 2.7 environment.

August 16, 2017

  * Add support for internal IP address load balancing.
  * Add support for configuring user and group management commands.
  * Improve security of authorized keys file writes.

July 18, 2017

  * Allow nologin paths other than /sbin/nologin.
  * Try to download GCS URLs with curl if gsutil is not installed.

June 09, 2017

  * Add a configuration option to disable IP alias support.
  * Support instance configuration using the google-instance-configs metadata
    key.

(bsiegert)