Ensure Open vSwitch can be installed on RHEL6.

 * RHEL6 does not include Open vSwitch in the default repos, but it
   is available via the RDO repo.  This patch automatically
   configures the RDO repo for RHEL6.
 * The openvswitch package is now listed as an rpm dependency to
   ensure it can be cached by a pre-built CI environment.

Change-Id: I8f93f53039cca4ff29bcb91720be7bb047b3ed8a
Merge "Ensure Open vSwitch can be installed on RHEL6."