Update wmi to use generated powershell command line

modules/exploits/windows/local/wmi.rb

@@ -93,7 +93,11 @@ class Metasploit3 < Msf::Exploit::Local
         end
 
         x = rand_text_alpha(rand(3)+3)
-        exec_cmd = "powershell.exe -nop -w hidden -c $#{x} = ''"
+        exec_cmd = generate__psh_command_line({
+          :noprofile => true,
+          :windowstyle => 'hidden',
+          :command => "$#{x} = ''"
+        })
         env_vars.each do |env|
           exec_cmd << "+$env:#{env}"
         end