In order to provision different variant types such as embedded and
server releases, it's required to grep the VARIANT and VARIANT_ID
variables of os-release.
Specifically from this commit:
56267336c7
Which adds the VARIANT_ID="atomic.host" in order to differentiate
between Fedora Server and container-centric Atomic Host releases.
This commit adds the accessability of VARIANT and VARIANT_ID in order
for Docker Machine to successfully provision different variants of Fedora
releases.
Signed-off-by: Charlie Drage <charlie@charliedrage.com>