Handle content objects better

The ``ExtendedToStreamDecorator`` now handles content objects with one
less packet - the last packet of the content has EOF set rather than
an empty packet with EOF set being sent.

Change-Id: If908c1fe8e6fbe2ac3834a1cd99e7cd8ace45b3b
We used to send (foo, eof=False), ('', eof=True) now we send (foo, eof=True)