Merge pull request dotless-de#436 from kubasov-s/installed-test

Fix unreliable test of installed guest additions

Author: fnordfish

lib/vagrant-vbguest/installers/linux.rb

@@ -77,7 +77,9 @@ def running?(opts=nil, &block)
         kmods = nil
         communicate.sudo('cat /proc/modules', opts) do |type, data|
           block.call(type, data) if block
-          kmods = data if type == :stdout && data
+          if type == :stdout && data
+            kmods = kmods.nil? ? data : kmods + data
+          end
         end
 
         unless kmods