bin/get-pick-list.sh: handle the fixes tag

Having a separate script to handle the fixes tag, brings a number of
issues, so let's fold it in get-pick-list.sh.

v2:
 - pass the sha as argument to the function
 - Keep original sed pattern

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Juan A. Suarez <jasuarez@igalia.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
(cherry picked from commit 181203f3)