Fixing Ubuntu's preseed URL mutation

The preseed's URL was not working in cases where the domain did not contain a
period. That happened due to a "feature" where the preseed/url kernel
argument would be augmented by the get_domain parameter of the node. For
example, if the policy's hostname pattern was "node${id}.example.com", the
preseed URL would be mutated from
"http://razor-server:8080/svc/file/preseed" to
"http://razor-server.example.com:8080/svc/file/preseed". This method grabs
the preseed file first, then passes it using preseed/file instead of
preseed/url.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-326
Fixing Debian's preseed URL mutation

The preseed's URL was not working in cases where the domain did not contain a
period. That happened due to a "feature" where the preseed/url kernel
argument would be augmented by the get_domain parameter of the node. For
example, if the policy's hostname pattern was "node${id}.example.com", the
preseed URL would be mutated from "http://razor-server:8080/svc/file/preseed"
to "http://razor-server.example.com:8080/svc/file/preseed". This method grabs
the preseed file first, then passes it using preseed/file instead of
preseed/url.

Fixes https://tickets.puppetlabs.com/browse/RAZOR-325