Fixes 4309

When the winrm communicator executes a command in an elevated shell,
this patch causes it to escape double quotes.

This is necessary as the first line in the file that it produces and
then executes it puts the command into a variable called command that
is delimited by double quotes.
Merge pull request #4313 from w3ttr3y/master

Fixes 4309: Error when provisioning Windows host using Puppet