This changes SSH Agent utilization from opt-in to opt-out, bringing
Terraform in line with the behavior of Packer and the `ssh` command
itself.
But skip SSH agent connections if the SSH_AUTH_SOCK env var doesn't exist,
whcih means there's no agent to connect to.
I added a debug log line in the last commit, only to find out it’s now
logging the same info twice. So removed the double entry and tweaked
the existing once.
While fixing the vet warning also tried to improve any feedback by
showing the actual output/error instead of just the error code.
While testing this I noticed only adding stderr output is not enough as
not all error info is send to stderr, but sometimes also to stdout.
* We now return an error when you set the script_path to
C:\Windows\Temp explaining this is currently not supported
* The fix in PR #1588 is converted to the updated setup in this PR
including the unit tests
Last thing to do is add a few tests for the WinRM communicator…
This is needed as preperation for adding WinRM support. There is still
one error in the tests which needs another look, but other than that it
seems like were now ready to start working on the WinRM part…