Separate head restrictions from get

We need to be able to allow head requests while disallowing get
requests. In swift, we want to be able to call head on the account
for metadata, but will be listing containers - both of which are calls
on the root URL - from a different class

Change-Id: Ic1488da60718e7d518c531d2f02b78a8b0c72c8d
Merge "Separate head restrictions from get"