terraform: fix Windows password injection in userdata_windows.tpl

Use single quotes for the SetPassword argument so PowerShell treats
the injected value literally. With double quotes, any $-containing
password (e.g. 'Io4$$WZy...') gets corrupted by PowerShell variable
expansion ($$ → PID, $WZy → empty var), causing the Windows instance
to boot with a different password than Launchpad holds → WinRM 401.

Terraform templatefile() substitutes ${windows_administrator_password}
before userdata reaches EC2, so single-quoting is safe: Terraform sees
and expands the ${} expression; PowerShell then receives the literal value
with no further interpretation.

Author: james-nesbitt

examples/terraform/aws-simple/userdata_windows.tpl

@@ -1,6 +1,6 @@
 <powershell>
 $admin = [adsi]("WinNT://./administrator, user")
-$admin.psbase.invoke("SetPassword", "${windows_administrator_password}")
+$admin.psbase.invoke("SetPassword", '${windows_administrator_password}')
 
 # Snippet to enable WinRM over HTTPS with a self-signed certificate
 # from https://gist.github.com/TechIsCool/d65017b8427cfa49d579a6d7b6e03c93