MINOR: thread: make wake_thread() take care of the sleeping threads mask

MINOR: thread: make wake_thread() take care of the sleeping threads mask

Almost every call place of wake_thread() checks for sleeping threads and
clears the sleeping mask itself, while the function is solely used for
there. Let's move the check and the clearing of the bit inside the function
itself. Note that updt_fd_polling() still performs the check because its
rules are a bit different.