- this change extends the tools/cleanup-containers script to
  support a grep extended regex as a first paramater.
- if tools/cleanup-containers is called with a grep extended
  regex string as a first paramater, only containers mataching
  that regex will be cleaned up.
- e.g. tools/cleanup-containers "neutron|openvswitch"
  will cleanup all container whoes name contains either neutron
  or openvswitch.

Change-Id: Iadb68c0a8de40e9ec2c0a27568e3a372ec0e8303
Closes-Bug: #1522168