fixes issue with installing vagrant plugins on vagrant 1.8.1 and ubuntu 16.04 (see http://stackoverflow.com/questions/36811863/cant-install-vagrant-plugins-in-ubuntu-16-04/36991648#36991648)

vagrant-plugin.patch

---
 lib/vagrant/bundler.rb | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/vagrant/bundler.rb b/lib/vagrant/bundler.rb
index 5a5c185..c4a3837 100644
--- a/lib/vagrant/bundler.rb
+++ b/lib/vagrant/bundler.rb
@@ -272,7 +272,6 @@ module Vagrant

       # Reset the all specs override that Bundler does
       old_all = Gem::Specification._all
-      Gem::Specification.all = nil

       # /etc/gemrc and so on.
       old_config = nil
@@ -286,6 +285,8 @@ module Vagrant
       end
       Gem.configuration = NilGemConfig.new

+      Gem::Specification.reset
+
       # Use a silent UI so that we have no output
       Gem::DefaultUserInteraction.use_ui(Gem::SilentUI.new) do
     return yield

sudo patch --directory /usr/lib/ruby/vendor_ruby/vagrant < vagrant-plugin.patch