Verified in 5.8.1.0.20170623170756_3ed4411. The UI accepts ssh urls like git:jonnyfiveiq/Ansible_Playbooks, but it seems the backend can't pull playbooks.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHSA-2017:1758