Allow binding apache to a specific IP address

Add a 'bind_host' parameter to keystone::wsgi::apache to allow binding
to a specific IP address.

Fixes Bug #1273697

Change-Id: I4e94336c15132900dbe42052e46d0c7f2e36f91f
Merge "Allow binding apache to a specific IP address"
Merge git://github.com/puppetlabs/puppetlabs-keystone