When I delete a current MNet Marhara host and try to add the same one, it fails with a message

"A record already exists for a host with that hostname (it may be deleted). click here to edit that record."

After I have deleted it and I navigate to Mnet Test client, the host i have deleted is still there

To replicate (the first issue with the link):

1. Set up Moodle-Mahara link as per https://docs.moodle.org/400/en/Mahoodle
2. Go to Site admin > Networking > Manage peers
3. Delete the Mahara peer
4. Now try to recreate the very same Mahara peer (URL must be the exact same)
5. Notice there's a validation message on the form:
   "A record already exists for a host with that hostname (it may be deleted). click here to edit that record."
6. Click the link
   Expected: You can edit the deleted host and mark it active again
   Actual: You see a 404 because of the unresolved "{$a}" in the URL.