(#9056) Pass ruby block to capture stdout when determining PS version

Prior to this commit, the function used to determine the version of
Powershell would loop forever inside the Subprocess.execute function
because the process would never exit. This commit fixes that by passing
in a ruby block to capture the version from stdout instead of trying to
capture it from the returned process when it exits.

lib/vagrant/util/powershell.rb

@@ -11,6 +11,7 @@ module Vagrant
     class PowerShell
       # NOTE: Version checks are only on Major
       MINIMUM_REQUIRED_VERSION = 3
+      LOGGER = Log4r::Logger.new("vagrant::util::powershell")
 
       # @return [Boolean] powershell executable available on PATH
       def self.available?
@@ -85,8 +86,14 @@ module Vagrant
             "Write-Output $PSVersionTable.PSVersion.Major"
           ].flatten
 
-          r = Subprocess.execute(*command)
-          @_powershell_version = r.exit_code != 0 ? nil : r.stdout.chomp
+          version = nil
+          begin
+            r = Subprocess.execute(*command, notify: [:stdout, :stderr], timeout: 10) {|io_name,data| version = data}
+          rescue Vagrant::Util::Subprocess::TimeoutExceeded
+            LOGGER.debug("Timeout exceeded while attempting to determine version of Powershell.")
+          end
+
+          @_powershell_version = version
         end
         @_powershell_version
       end