Update test-release.bash to use public repo, instead of working copy.

The test systems clones the repo in a way that doesn't work so well with this
test. Remove the CHPL_HOME_REPOSITORY var, so gen_release will simply clone
from the github repo.
Merge pull request #415 from thomasvandoren/update-test-release-script

Update test-release.bash to use public repo, instead of working copy.

The test systems clones the repo in a way that doesn't work so well with this
test. Remove the CHPL_HOME_REPOSITORY var, so gen_release will simply clone
from the github repo.