(#8743) Fix puppet provisioner by removing manifestdir flag

Prior to this commit, the puppet provisioner would use the manifest dir
flag when running `puppet apply`. Not only is this flag redundant due to
how puppet apply works, but it is also deprecated in Puppet 4 and
removed in Puppet 5. This commit simply removes the flag when invoking
`puppet apply`.

plugins/provisioners/puppet/provisioner/puppet.rb

@@ -199,8 +199,6 @@ module VagrantPlugins
           if config.environment_path
             options << "--environmentpath #{environments_guest_path}/"
             options << "--environment #{@config.environment}"
-          else
-            options << "--manifestdir #{manifests_guest_path}"
           end
 
           options << @manifest_file

test/unit/plugins/provisioners/puppet/provisioner/puppet_test.rb

@@ -0,0 +1,51 @@
+require File.expand_path("../../../../../base", __FILE__)
+
+require Vagrant.source_root.join("plugins/provisioners/puppet/provisioner/puppet")
+
+describe VagrantPlugins::Puppet::Provisioner::Puppet do
+  include_context "unit"
+
+  let(:iso_env) do
+    # We have to create a Vagrantfile so there is a root path
+    env = isolated_environment
+    env.vagrantfile("")
+    env.create_vagrant_env
+  end
+
+  let(:machine) { iso_env.machine(iso_env.machine_names[0], :dummy) }
+  let(:config)       { double("config") }
+  let(:facts)        { [] }
+  let(:communicator) { double("comm") }
+  let(:guest)        { double("guest") }
+  let(:comm) { VagrantTests::DummyCommunicator::Communicator.new(machine) }
+  let(:module_paths) { ["etc/puppet/modules"] } # make this something real
+
+  subject { described_class.new(machine, config) }
+
+  before do
+    allow(machine).to receive(:communicate).and_return(comm)
+  end
+
+  describe "#run_puppet_apply" do
+    let(:options) { double("options") }
+    let(:binary_path) { "/opt/puppetlabs/bin" }
+    let(:manifest_file) { "default.pp" }
+
+    it "runs puppet on a manifest" do
+      allow(config).to receive(:options).and_return(options)
+      allow(config).to receive(:environment_path).and_return(false)
+      allow(config).to receive(:facter).and_return(facts)
+      allow(config).to receive(:binary_path).and_return(binary_path)
+      allow(config).to receive(:environment_variables).and_return(nil)
+      allow(config).to receive(:working_directory).and_return(false)
+      allow(config).to receive(:manifest_file).and_return(manifest_file)
+
+      allow_message_expectations_on_nil
+      allow(@module_paths).to receive(:map) { module_paths }
+      allow(@module_paths).to receive(:empty?).and_return(true)
+
+      expect(machine).to receive(:communicate).and_return(comm)
+      subject.run_puppet_apply()
+    end
+  end
+end