vty_test_runner.py: fix indents to use spaces, fix vim comment

Most of this file uses four spaces of indenting. Replace all tabs with spaces.

Remove the erratic 'set' from the recently added vim comment at the bottom.

Change-Id: I4273b3314defb1e5b31b509c2ac7d7c6cd6834cf

openbsc/tests/vty_test_runner.py

@@ -1360,4 +1360,4 @@ if __name__ == '__main__':
     res = unittest.TextTestRunner(verbosity=verbose_level, stream=sys.stdout).run(suite)
     sys.exit(len(res.errors) + len(res.failures))
 
-# vim: set shiftwidth=4 expandtab nocin ai
+# vim: shiftwidth=4 expandtab nocin ai