Slight tweak to avoid PowerShell 3.0 bug

There are some bugs in the PowerShell 3.0 engine which produce "executable script code found in signature block" errors even when there is no signature block.  Interestingly, this bug appears to be triggered when passing a string value to Set-Item in the function provider, but [scriptblock]::Create() works fine (and the resulting script block can be passed to Set-Item just fine.)