I have the same problem and see the same log entries in the /var/log/vmware/rbd/rbd-cgi.log file. I was trying to re-deploy the host using auto deploy after upgrading VCSA from 6.0U3 to 6.7U2c, I even tried removing the host from the vCenter server's inventory but still the same problem, it gets stuck downloading waiter.tgz.

There seems to be a problem with the new certificate that tries to issue when host gets re-deployed. I've checked using the certool with the following command and I see there is still a certificate for that host that wasn't deleted when I removed it from the inventory:

/usr/lib/vmware-vmca/bin/certool --enumcert --filter=all | less

Edit: I've tried re-deploying the host after restarting the Auto Deploy waiter service, I also rebooted the VCSA once after removing the ESXi host from the inventory but it still gets stuck at the same step of the deployment.