Use shortened version in order to avoid revision/arch mishaps.

Sometimes -X is added to package names which does not exist in the
/version file. Simply using the version string does not work on
RHEL (it does on centos). Until version and the packages match
identically we instead will just split the version at the - and
no longer specify the dist for better reliability but slightly
lower accuracy.

Signed-off-by: Sandon Van Ness <sandon@inktank.com>
Merge pull request #153 from ceph/wip-6790

Reviewed by Warren.