[COOK-2574] Add CAS authentication to apache proxy.
[COOK-2574] make basic auth optional for apache proxy
Merge branch 'COOK-2574'
[test-kitchen] ensure a host-only network is configured
[test-kitchen] add test suites for http proxy recipes
change optional cookbooks from 'suggests' to 'depends'

Chef 11 only loads attributes from dependent cookbooks correctly if a
proper depends exists.