Replace NoTarget with NotVulnerable

Author: bcoles

modules/exploits/windows/http/serviio_checkstreamurl_cmd_exec.rb

@@ -95,7 +95,7 @@ def execute_command(cmd, opts = {})
   end
 
   def exploit
-    fail_with(Failure::NoTarget, 'Target is not vulnerable') unless check == CheckCode::Appears
+    fail_with(Failure::NotVulnerable, 'Target is not vulnerable') unless check == CheckCode::Appears
     execute_cmdstager(:temp => '.', :linemax => 8000)
   end
 end