refs #7264 - only check for java 1.7.0

'yum install katello' will now pull in 1.7.0; therefore, without
this change, both 1.6.0 and 1.7.0 were getting installed on centos
and rhel.

Removing the 1.6.0 check since that is no longer needed.
Merge pull request #3 from bbuckingham/issue-7264

refs #7264 - only check for java 1.7.0