Memory leak on the write_buffer for HTTP/2

                                          Location |          Size In-use
---------------------------------------------------+------------------------
                    memory/IOBuffer/./FetchSM.h:62 |                    0
                    memory/IOBuffer/./FetchSM.h:64 |                    0
                  memory/IOBuffer/PluginVC.cc:1013 |                    0
                  memory/IOBuffer/PluginVC.cc:1016 |                    0
          memory/IOBuffer/HttpClientSession.cc:211 |                    0
                    memory/IOBuffer/HttpSM.cc:5723 |                    0
                    memory/IOBuffer/HttpSM.cc:6275 |                    0
           memory/IOBuffer/HttpServerSession.cc:86 |                 8192
                 memory/IOBuffer/HttpTunnel.cc:111 |                    0
         memory/IOBuffer/Http2ClientSession.cc:134 |                    0
         memory/IOBuffer/./Http2ClientSession.h:96 |                16384  <--- tracked here
          memory/IOBuffer/SSLNetVConnection.cc:520 |                    0
       memory/IOBuffer/./P_SSLNetVConnection.h:203 |                    0
                                             TOTAL |                24576