don't lock file when calculating checksum

lib/ansible/module_utils/powershell.ps1

@@ -211,7 +211,7 @@ Function Get-FileChecksum($path)
     If (Test-Path -PathType Leaf $path)
     {
         $sp = new-object -TypeName System.Security.Cryptography.SHA1CryptoServiceProvider;
-        $fp = [System.IO.File]::Open($path, [System.IO.Filemode]::Open, [System.IO.FileAccess]::Read);
+        $fp = [System.IO.File]::Open($path, [System.IO.Filemode]::Open, [System.IO.FileAccess]::Read, [System.IO.FileShare]::ReadWrite);
         $hash = [System.BitConverter]::ToString($sp.ComputeHash($fp)).Replace("-", "").ToLower();
         $fp.Dispose();
     }