scripts: change scripts to use system python instead of env

Just a small change to a couple of scripts to go from

 #!/usr/bin/env python

to

 #!/usr/bin/python

This shouldn't effect anyone, unless they don't install python there.

In preparation for python3, Fedora is doing a big push to change the scripts
to use the system python.  This allows developers to put the python3 in
their path without fear of breaking existing scripts.

Now I am pretty sure anyone using python3 for testing purposes will probably
not run any of the scripts I changed, but Fedora has this automated tool
that checks for this stuff so I thought I would try to push it upstream.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: WANG Cong <xiyou.wangcong@gmail.com>
Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

arch/ia64/scripts/unwcheck.py

-#!/usr/bin/env python
+#!/usr/bin/python
 #
 # Usage: unwcheck.py FILE
 #

scripts/rt-tester/rt-tester.py

-#!/usr/bin/env python
+#!/usr/bin/python
 #
 # rt-mutex tester
 #

scripts/show_delta

-#!/usr/bin/env python
+#!/usr/bin/python
 #
 # show_deltas: Read list of printk messages instrumented with
 # time data, and format with time deltas.