Merge r1554995 from trunk:

Providers defined in <AuthnProviderAlias have not been usable under
in virtual hosts since migrating from mod_authn_alias to mod_authn_core.
PR 55622.


Submitted by: covener
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1556818 13f79535-47bb-0310-9956-ffa450edef68