(PUP-3302) Puppet resource fails when using directory environments

Before this fix when `puppet resource file` was being used set with
source defined puppet would fail and raise an an EnvironmentNotFound
error.

@jpartlow and I dug in and investigated why this error was being raised
and found that it was because we need an environment object
in Puppet::Indirector::Request#environment= and instead of the
none environment being passed around it is passed as the string "none"
which is a directory environment that does not exist. This is what is
raising the EnvironmentNotFound error in puppet.

Instead of passing around a string we pass around the none environment
to fix the issue.
This will be subject to breakage if puppet ever changes the default checksum, which we are likely to do.

What is the purpose of this? Is it simply to check that the file got written correctly? If so, maybe it would be better to read the file from the remote system and check the contents?