tools: use /usr/bin/python2.7 as the interpreter

Distros such as Fedora
(https://fedoraproject.org/wiki/Packaging:Python#Multiple_Python_Runtimes
) are clamping down on python interpreter paths due to the desire to
switch to python3 so /usr/bin/python or /usr/bin/env python are no
longer liked. Unfortunately macOS doesn't ship a /usr/bin/python2 link
so switch all python interpreter paths to /usr/bin/python2.7 as a
compromise.

Signed-off-by: Sitsofe Wheeler <sitsofe@yahoo.com>

tools/fio_jsonplus_clat2csv

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python2.7
 #
 # fio_jsonplus_clat2csv
 #

tools/fiologparser.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python2.7
 #
 # fiologparser.py
 #
@@ -218,4 +218,3 @@ def get_contribution(self, start, end):
         print_all_stats(ctx, series)
     else:
         print_default(ctx, series)
-

tools/hist/fiologparser_hist.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2.7
+#!/usr/bin/python2.7
 """ 
     Utility for converting *_clat_hist* files generated by fio into latency statistics.
     

tools/hist/half-bins.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2.7
+#!/usr/bin/python2.7
 """ Cut the number bins in half in fio histogram output. Example usage:
 
         $ half-bins.py -c 2 output_clat_hist.1.log > smaller_clat_hist.1.log
@@ -35,4 +35,3 @@ def main(ctx):
             'e.g. coarseness of 4 merges each 2^4 = 16 consecutive '
             'bins.')
     main(p.parse_args())
-

tools/plot/fio2gnuplot

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python2.7
 #
 #  Copyright (C) 2013 eNovance SAS <licensing@enovance.com>
 #  Author: Erwan Velu  <erwan@enovance.com>

unit_tests/steadystate_tests.py

@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python2.7
 #
 # steadystate_tests.py
 #