The rhel7 element is deprecated and is left only for backward
compatibility.
The rhel element should be used instead. Users should set DIB_RELEASE to
'7' to indicate which release you are using.
The new element is a version-less RHEL element to handle both '7'
and '8' DIB_RELEASE, which aligns with other elements which operate in
the same way such as the Fedora element.
Change-Id: Ic39ed85cacae9942448eb18ad685763f9369c2ed
