CHEF-5198: add func tests for remote_file

this tests:

- successful uncompressed downloads with correct content-length
- successful compressed downloads with correct content-length
- unsuccessful uncompressed downloads with incorrect content-length
- unsuccessful compressed downloads with incorrect content-length
- successful downloads with incorrect conteng-length when
  transfer-encoding is set

this makes sure that decompression + content length validate is
happening in the correct order with remote_file and that we're ignoring
the content-length in the presence of a transfer-encoding.
Merge pull request #1370 from opscode/lcg/CHEF-5198-remote-file-functests

CHEF-5198: add func tests for remote_file