(2.6)dcache: httpd service, remove ipv4 specific binding

The Jetty ssl connector was hardcoded to listen on "0.0.0.0".  This is an ipv4-specific mask.  The simple connector and the ssl connector also did not allow for a different net binding.

This patch removes the hardcoded binding of host name and exposes an httpd.net.listen property which defaults to dcache.net.listen.

Since new properties cannot be ported to 2.6, a separate patch which simply removes the hard-coded ipv4 setting will be provided.

Testing:

Checked that the default settings still work.

Target: 2.6
Patch: http://rb.dcache.org/r/6116
Require-notes: yes
Require-book: no
Acked-by: Gerd
Committed: 4c32223de86e57ef42c0052c024f81b6187a504a

RELEASE NOTES:
Allows for ipv6 binding of httpd service.