Adjust acl option yaml input syntax

[mjbnz]

Having an acl entry requiring a single dictionary member called string seemed a little superfluous, so this patch adjusts the accepted syntax to include the following two examples, but also retain the string member format.

As an array of strings:

haproxy_frontend:
  - name: 'be-http'
    ....
    acl:
      - "is_foo hdr(host) -i foo.com"
      - "is_bar hdr(host) -i bar.com"

As a dictionary of named rules:

haproxy_backend:
  - name: 'be-http'
    ....
    acl:
      is_foo: "hdr(host) -i foo.com"
      is_bar: "hdr(host) -i bar.com"

[mjbnz]

Hello, any chance that this PR might be accepted?

[tersmitten]

This looks backwards compatible, am I correct?

[tersmitten]

What's up with the | default(acl)?