Change from comma separated list of memcache servers to space separated list.
Comma seperated list results in a 500 error response.
Upstream docs state this should be space separated and can be found here:
https://github.com/zmartzone/mod_auth_openidc/blob/master/auth_openidc.conf#L629-L631

Closes-Bug: #1972033
Change-Id: Ibaef3672c656213dd5ba1488379d686130e041c5