providers/docker: remove synced folders after docker rm

plugins/guests/linux/cap/mount_virtualbox_shared_folder.rb

@@ -79,6 +79,14 @@ module VagrantPlugins
               "/sbin/initctl emit --no-wait vagrant-mounted MOUNTPOINT=#{expanded_guest_path}")
           end
         end
+
+        def self.unmount_virtualbox_shared_folder(machine, guestpath, options)
+          result = machine.communicate.sudo(
+            "umount #{guestpath}", error_check: false)
+          if result == 0
+            machine.communicate.sudo("rm -rf #{guestpath}", error_check: false)
+          end
+        end
       end
     end
   end

plugins/guests/linux/plugin.rb

@@ -70,6 +70,11 @@ module VagrantPlugins
         require_relative "cap/rsync"
         Cap::RSync
       end
+
+      guest_capability("linux", "unmount_virtualbox_shared_folder") do
+        require_relative "cap/mount_virtualbox_shared_folder"
+        Cap::MountVirtualBoxSharedFolder
+      end
     end
   end
 end

plugins/providers/docker/action/host_machine_sync_folders_disable.rb

@@ -17,28 +17,28 @@ module VagrantPlugins
         def call(env)
           return @app.call(env) if !env[:machine].provider.host_vm?
 
+          # Read our random ID for this instance
+          id_path   = env[:machine].data_dir.join("host_machine_sfid")
+          return @app.call(env) if !id_path.file?
+          host_sfid = id_path.read.chomp
+
           host_machine = env[:machine].provider.host_vm
 
+          @app.call(env)
+
           begin
             env[:machine].provider.host_vm_lock do
-              setup_synced_folders(host_machine, env)
+              setup_synced_folders(host_machine, host_sfid, env)
             end
           rescue Vagrant::Errors::EnvironmentLockedError
             sleep 1
             retry
           end
-
-          @app.call(env)
         end
 
         protected
 
-        def setup_synced_folders(host_machine, env)
+        def setup_synced_folders(host_machine, host_sfid, env)
-          # Read our random ID for this instance
-          id_path   = env[:machine].data_dir.join("host_machine_sfid")
-          return if !id_path.file?
-          host_sfid = id_path.read.chomp
-
           to_disable = []
 
           # Read the existing folders that are setup

plugins/providers/virtualbox/synced_folder.rb

@@ -67,7 +67,13 @@ module VagrantPlugins
       end
 
       def disable(machine, folders, _opts)
-        # TODO: unmount.
+        if machine.guest.capability?(:unmount_virtualbox_shared_folder)
+          folders.each do |id, data|
+            machine.guest.capability(
+              :unmount_virtualbox_shared_folder,
+              data[:guestpath], data)
+          end
+        end
 
         # Remove the shared folders from the VM metadata
         names = folders.map { |id, _data| os_friendly_id(id) }