Remove dangerous reference

Remove dangerous reference

RequestContext contained reference to an external BinaryQueue. One
problem was, BBQ was held inside vector (so practically any operation
on vector made this object out-of-date), second problem was,
RequestContext was passed to other classes inside shared_ptr, so owner
of this bbq looses control other its reference.
Moreover, soon RequestContext will be held pending (e.g. when waiting
for external Agent to return answer) inside cynara logic, so BBQ stored
inside RequestContext needs to be alive as long as corresponding
connection is opened. Not more, not less.

Change-Id: I79c9eb9b5e74927bd7bb159da01fae23612ca83e