Wakka::HasAccess doesn't honor $username parameter

[skrap]

Wakka::HasAccess doesn't honor $username parameter. Instead, in several places, it uses the currently logged-in user.

There's a @todo which might cover this, but I don't understand its comment about IP addresses, so I've not removed it.

Here's a patch to address this bug.

[BrianKoontz]

(In[1884]) Recognizes and handles $username if passed in as an argument. Refs #1136