Fix synchronous readline "\n" handling.
Fix synchronous readline "\n" handling.

Our function to read a line with a timeout handles newlines as requests
to refresh the timeout, however the code kept subtracting the buffer
size left every time a newline was received, for a bug in the loop
logic. Fixed by this commit.

JackieXie168/redis,JackieXie168/redis,JackieXie168/redis,JackieXie168/redis