Without a seed, the "random" script path locations for the remote-exec
provisioner were actually deterministic!
Every rand.Int31() would return the same pseudorandom chain starting w/
the numbers: 1298498081, 2019727887, 1427131847, 939984059, ...
So here we properly seed the communicators so the script paths are
actually random, and multiple runs on a single remote host have much
less chance of clobbering each other.
Fixes#4186
Kudos to @DustinChaloupka for the correct hunch leading to this fix!
Pretty nice test coverage this way, covering all WinRM actions/logic by
using the winrmtest package. I had to extend/update/fix that package a
little here and there, but it now serves a nice purpose for testing
WinRM stuff…
* 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…