Don't use hash with indifferent access when converting hash

The HashWithIndifferentAccess will change all keys to strings when
merged with another regular hash. This causes errors in cases where
hashes are merged, for example in the action builder. Symbol/String
type data is kept over the wire, so there is no need to make the
mapped hash a HashWithIndifferentAccess.

plugins/commands/serve/mappers/known_types.rb

@@ -171,7 +171,7 @@ module VagrantPlugins
 
         def converter(proto, mapper)
           begin
-            h = Hash.new.tap do |result|
+            Hash.new.tap do |result|
               proto.entries.each do |entry|
                 # Convert our key and value to native types
                 k = mapper.map(entry.key)
@@ -183,7 +183,6 @@ module VagrantPlugins
                 result[k] = v
               end
             end
-            Vagrant::Util::HashWithIndifferentAccess.new(h)
           rescue => err
             logger.error { "proto mapping to hash failed: #{err}" }
             raise