refactor(proxy): remove _potential_ deadlock
The dc.Send() should increase the bufferedAmount value,
so there is no need to add the message length a second time.
Also replace GT with GE, for the case where
BufferedAmountLowThreshold === maxBufferedAmount
Currently the deadlock cannot happen because maxBufferedAmount
and BufferedAmountLowThreshold are too far apart, in fact
the former is 2x the latter.
See