git.detached: Fix traceback when rev is a SHA and is not present locally
git.detached: Fix traceback when rev is a SHA and is not present locally

This catches the (expected) CommandExecutionError when git.describe is
run on a commit that doesn't exist.

This also renames the remote_ref_type variable to remote_rev_type. This
change was made for the 2017.7 branch, but this fix is being applied to
2016.11, so by making the rename here as well we will avoid a potential
bug from creeping in on a merge-forward.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt