Currently the latest RDO repo is installed on centos9
for the python-hardware package. This would not be appropriate in the
following cases:
* When repos are copied in from the host via DIB_YUM_REPO_CONF
* When another element is responsible for setting up repos
This change adds environment variable DIB_IPA_HARDWARE_RDO, which will
only be set to `1` on centos9, when DIB_YUM_REPO_CONF isn't set, and
when the user hasn't explicitly set DIB_IPA_HARDWARE_RDO.
This retains the current default behaviour of just working, while
giving flexibility for repos to be set up another way.
Change-Id: I1cc0b9833baf642866e9762c6bae44360bffe20d
cb216b6cd8