Enable retries when fetching container state

Fixes #74

lib/vagrant-lxc/driver/cli.rb

@@ -39,7 +39,7 @@ module Vagrant
         end
 
         def state
-          if @name && run(:info, '--name', @name) =~ /^state:[^A-Z]+([A-Z]+)$/
+          if @name && run(:info, '--name', @name, retryable: true) =~ /^state:[^A-Z]+([A-Z]+)$/
             $1.downcase.to_sym
           elsif @name
             :unknown

spec/unit/driver/cli_spec.rb

@@ -126,7 +126,7 @@ describe Vagrant::LXC::Driver::CLI do
 
     it 'calls lxc-info with the right arguments' do
       subject.state
-      subject.should have_received(:run).with(:info, '--name', name)
+      subject.should have_received(:run).with(:info, '--name', name, retryable: true)
     end
 
     it 'maps the output of lxc-info status out to a symbol' do