Fix PowerShell System.UnauthorizedAccessException issue when execute RunSamples.cmd

[tawan0109]

• When executed RunSample.cmd on WIndows 10 (Version 10.0.10240 by ver command), following error happened:

  D:\SparkWorkspace\SparkCLR>RunSamples.cmd --validate
  SPARK_VERSION=1.4.1
  HADOOP_VERSION=2.6
  Set-ExecutionPolicy : Access to the registry key
  'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PowerShell\1\ShellIds\Microsoft.PowerShell' is denied. To change the execution
  policy for the default (LocalMachine) scope, start Windows PowerShell with the "Run as administrator" option. To
  change the execution policy for the current user, run "Set-ExecutionPolicy -Scope CurrentUser".
  At line:1 char:1
  > + Set-ExecutionPolicy Unrestricted
  > + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  >    + CategoryInfo          : PermissionDenied: (:) [Set-ExecutionPolicy], UnauthorizedAccessException
  >    + FullyQualifiedErrorId : System.UnauthorizedAccessException,Microsoft.PowerShell.Commands.SetExecutionPolicyComma
  nd
  [downloadtools] hadoopVersion=2.6, sparkVersion=1.4.1
  [Download-BuildTools] D:\SparkWorkspace\SparkCLR\tools\TarTool.exe exists already. No download and extraction needed
  ...
  

• Explicitly set the scope to CurrentUser to avoid this exception.

[skaarthik]

LGTM