support passing in alternative URLs for job or buildinfo.json when running getProjectSHAs.sh

This build shows that the check is looking in one place but the update site is in another:

• https://dev-platform-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/jbosstools-releng-push-to-staging-01-check-versions-branches-root-poms/23/console

• http://download.jboss.org/jbosstools/oxygen/snapshots/builds/jbosstools-integration-tests.aggregate_master/latest/all/repo/buildinfo.json vs.
• http://download.jboss.org/jbosstools/neon/snapshots/builds/jbosstools-integration-tests_master/latest/all/repo/buildinfo.json

Also, Fuse is built on another server:

• https://fusesource-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/view/Fuse%20Tooling/job/jbosstools-fuse_master/ vs.
• https://dev-platform-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/jbosstools-fuse_master/

So, we should be able to configure alternative URLs for the job or the download.jboss.org path.