LSB Release is not installed by default on minimal OS installs (for example cloud...

LSB Release is not installed by default on minimal OS installs (for example cloud-images). Script fails with a "command not found" erroor.
Checking if lsb_release is present BEFORE doing the test
Change os_VERSION to grab the major OS version instead of the distro codename
When installing EPEL, use $os_VERSION to grab the correct rpm instead of using hardcoded '7' package that would fail on other versions.
os_Version can also be use to deprecate old version on which ceph-ansible is not supported.