Removed 'prerelease' and 'release' routes.

We will never use osg-promote to promote to prerelease/release.

git-svn-id: file:///p/vdt/workspace/svn/software/osg-build/trunk@17679 4e558342-562e-0410-864c-e07659590f8c
Fix exception handling in get_latest_build

git-svn-id: file:///p/vdt/workspace/svn/software/osg-build/trunk@17680 4e558342-562e-0410-864c-e07659590f8c