Filemanager link in admin doesn't lead to FM admin

[rgaudin]

Admin UI links to resources.FQDN/admin/?p= but when one follows this and logs in, one ends up at resources/FQDN/?p= so not in the admin part of the file manager.

Works OK on actual hotspot.

Example: http://resources.medical.demo.hotspot.kiwix.org/admin/?p=

See #17