CLEANUP: stream: remove unneeded test on appctx during initialization

CLEANUP: stream: remove unneeded test on appctx during initialization

Now that the data consumption from the endpoint is the default setting,
we can generalize the pre-clearing of the wont_consume flag, which is
no more specific to applets. In practice it's not needed anymore to do
it, but since streams might be initiatied from asynchronous applets,
these might have blocked their consumption side before creating the
stream thus it's safer to preserve the clearing of the flag.