Do not use compression in tornado httpclient requests
Do not use compression in tornado httpclient requests

Tornado releases since 4.0 have a ``decompress_response`` argument
(defaulting to ``True``), which causes any gzip'ed data downloaded in a
tornado HTTPClient request to be decompressed after being downloaded.
Tar archives compressed using gzip therefore end up being decompressed,
which causes errors in ``file.managed`` states as hash verification
fails.

Using ``decompress_response=False`` in the client request resolves this.

This commit also makes the instantiaton of the tornado HTTPClient
instance DRY by not invoking the entire fetch command twice (once if
``max_body_size`` is supported, once if not).

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt