Fix a memory leak when the connection is closed either explicitly or due to pool cleanups.
Fix a memory leak when the connection is closed either explicitly or due to
pool cleanups.

This makes serf_connection_close match reset_connection which already did
this properly.

* outgoing.c
  (serf_connection_close): Destroy the ostream as well.

jandre/serf,jandre/serf,jandre/serf,jandre/serf