fix issue returning typed nil pointers

These functions returned typed pointers as their data field. Template
execution didn't like these typed nil pointer values when looking up
data on them. Changing them to return untyped pointers with an function
signature returning interface{} fixes this as the template knows to have
these always return `<no value>`.

Port of consul-template fix.
PR: #1535

remove some redudancy and add query options

Change fake deps to store saved QueryOptions to enables testing their
being set properly.