Remove find_stack_traces.py
Remove find_stack_traces.py

This commit removes find_stack_traces because the script looks a bit
rotten. For example, it doesn't care about the current 'Guide to
Devstack Gate Logs' page anymore. And this script isn't used any other
projects. One concern is that there are users who are executing this
script by hand. However, this script doesn't work correctly so far. So,
I think users should stop to use this script.

Change-Id: I8b82b3594c94c22e560300a4128f56d5274e082f

masayukig/tempest,openstack/tempest,openstack/tempest,masayukig/tempest,cisco-openstack/tempest,cisco-openstack/tempest