info-provider: Fix regression caused by info-provider using a deprecated property

Introduces the new property 'info-provider.http.port', which defines
the TCP port the info-provider will contact the httpd service on.

Sites that previously relied on redefining httpdPort will have to
set this new info-provider property.

Also fixed a bug that caused the HTTP_PORT and HTTP_HOST environment
variables to be ignored by the info-provider.

Target: trunk
Require-notes: no
Require-book: no
Request: 2.7
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6217/