Making call to DnsRequest more explicit.

Use DNS native Type for qtype when calling DnsRequest()

On a poorly configured apache, it seems the unicode literal that we pass as
qtype doesn't get converted correctly. This saves the internal DNS code from
having to do the conversion from string to int and is more robust against
poorly configured apache mod_wsgi setups.

Bugs closed: 3656

Reviewed at https://reviews.reviewboard.org/r/6552/