Fix handling of non-fatal lxc-stop return code

Fixes #405

lib/vagrant-lxc/driver/cli.rb

@@ -85,9 +85,20 @@ module Vagrant
           run :start, '-d', '--name', @name, *Array(options)
         end
 
+        ## lxc-stop will exit 2 if machine was already stopped
+        # Man Page:
+        # 2      The specified container exists but was not running.
         def stop
           attach '/sbin/halt' if supports_attach?
-          run :stop, '--name', @name
+          begin
+            run :stop, '--name', @name
+          rescue LXC::Errors::ExecuteError => e
+            if e.exitcode == 2
+               @logger.debug "Machine already stopped, lxc-stop returned 2"
+            else
+		raise e
+            end
+          end
         end
 
         def attach(*cmd)

lib/vagrant-lxc/errors.rb

@@ -5,12 +5,13 @@ module Vagrant
     module Errors
       class ExecuteError < Vagrant::Errors::VagrantError
         error_key(:lxc_execute_error)
-        attr_reader :stderr, :stdout
+        attr_reader :stderr, :stdout, :exitcode
         def initialize(message, *args)
           super
           if message.is_a?(Hash)
             @stderr = message[:stderr]
             @stdout = message[:stdout]
+            @exitcode = message[:exitcode]
           end
         end
       end

lib/vagrant-lxc/sudo_wrapper.rb

@@ -49,7 +49,7 @@ module Vagrant
               @logger.info("Exit code != 0, but interrupted. Ignoring.")
             else
               raise LXC::Errors::ExecuteError,
-                command: command.inspect, stderr: r.stderr, stdout: r.stdout
+                command: command.inspect, stderr: r.stderr, stdout: r.stdout, exitcode: r.exit_code
             end
           end
         end