Project client and proc mapper fixes

Default the options for default provider so an options value is not
required when calling. The index for the proc lookup should use the key
method, not index.

plugins/commands/serve/client/project.rb

@@ -54,7 +54,7 @@ module VagrantPlugins
           resp.path
         end
 
-        def default_provider(opts)
+        def default_provider(opts={})
           req = ::Hashicorp::Vagrant::Sdk::Project::DefaultProviderRequest.new(
             exclude: opts.fetch(:exclude, []),
             force_default: opts.fetch(:force_default, true),

plugins/commands/serve/mappers/proc.rb

@@ -19,7 +19,7 @@ module VagrantPlugins
             end
 
             # If this is already stored, return existing ID
-            idx = @stored.index(value)
+            idx = @stored.key(value)
             return idx if idx
 
             # Create a new ID and store