force http2 new parser on connection reset

lib/httpx/connection.rb

@@ -358,6 +358,8 @@ module HTTPX
 
         @io.close
         @read_buffer.clear
+        @parser.reset if @parser
+
         remove_instance_variable(:@timeout) if defined?(@timeout)
       when :already_open
         nextstate = :open

lib/httpx/connection/http2.rb

@@ -30,6 +30,10 @@ module HTTPX
       init_connection
     end
 
+    def reset
+      init_connection
+    end
+
     def close
       @connection.goaway unless @connection.state == :closed
     end