Fix Type::Booleans leaking through capabilities

We had some cases where calling a capability that returned a boolean was
not getting correctly unpacked, so instead of `true` or `false` the
capability was putting out
`VagrantPlugins::CommandServe::Type::Boolean`.

This may have been happening in _all_ cases where a boolean was returned
from a capability and we just didn't notice it yet because the return
value was always truthy.

These tweaks should help ensure that Ruby types make it out where they
are supposed to be in Args::Direct usage.

plugins/commands/serve/client/capability_platform.rb

@@ -35,15 +35,15 @@ module VagrantPlugins
               name: cap_name,
             )
           )
-          cb = proc do |name, args|
+          cb = lambda do |name, args|
             result = client.capability(
               SDK::Platform::Capability::NamedRequest.new(
                 name: name,
                 func_args: args,
               )
             )
-            return nil if result.nil?
-            mapper.map(result.result)
+            return nil if result.nil? || result.result.nil?
+            mapper.map(SDK::Args::Direct.new(arguments: [result.result])).arguments.first
           end
           [spec, cb]
         end

plugins/commands/serve/util/direct_conversions.rb

@@ -373,7 +373,10 @@ end
 class Hashicorp::Vagrant::Sdk::Args::Direct
   def to_ruby
     VagrantPlugins::CommandServe::Type::Direct.new(
-      arguments: arguments.map(&:to_ruby)
+      arguments: arguments.map { |arg|
+        val = arg.to_ruby
+        val.is_a?(VagrantPlugins::CommandServe::Type) ? val.value : val
+      }
     )
   end
 end