(#18162) Honor fileserver SRV record for file metadata requests

File content requests uses the x-puppet-fileserver SRV record, but file
metadata requests used the x-puppet SRV record.

Adds test for the functionality.
Merge branch 'dalen-file_metadata_srv'

* dalen-file_metadata_srv:
  (#18162) Honor fileserver SRV record for file metadata requests