CLEANUP: proto: rename TID affinity callbacks

CLEANUP: proto: rename TID affinity callbacks

Since the following patch, protocol API to update a connection TID
affinity has been extended.
  commit 1a43b9f32c71267e3cb514aa70a13c75adb20742
  MINOR: proto: extend connection thread rebind API

The single callback set_affinity has been splitted in 3 different
functions which are called at different stages during listener_accept(),
depending on accept queue push success or not. However, the naming was
rendered confusing by the usage of function prefix 1 and 2.

Rename proto callback related to TID affinity update and use the
following names :

* bind_tid_prep
* bind_tid_commit
* bind_tid_reset

This commit should probably be backported at least up to 3.0 with the
above patch. This is because the fix was recently backported and it
would allow to keep changes minimal between the two versions. It could
even be backported up to 2.8 if there is no major conflict.

(cherry picked from commit 9fbe8b03346a98cc8cc7b47eaa68935b1d4b3916)
Signed-off-by: Willy Tarreau <w@1wt.eu>