Fix problem in AudioFlinger closeOutput and closeInput.

There was no garanty that the corresponding thread destructor had been already called when exiting the closeOutput() or closeInput() functions.
This contructor could be called by the thread after the exit condition is signalled. By way of consequence, closeOutputStream() could be called after
we exited closeOutput() function.

To solve the problem, the call to closeOutputStream() or closeInputStream() is moved to closeOutput() or closeInput().