(maint) Change PE3 File location

Prior to this commit, the place where the harness was looking for PE3
was returning 404. This commit changes things by pointing to the
pe-release url.
(maint) Clean yum

Prior to this commit, there was an issue with the PE installer not being
able to get the packages it needs. This commit adds 'yum clean all' to
the wipe pe script to help prevent that state.
Merge pull request #63 from briancain/maint/master/yum_clean_all_add

Maint/master/yum clean all add