[FIX] Packaging: RedHat: (post-)install shell shebang

setup/redhat/install.sh

-#!/usr/bin/env bash
+#!/bin/sh
 set -e
 python setup.py install --prefix=/usr --root=$RPM_BUILD_ROOT --record=INSTALLED_FILES

setup/redhat/postinstall.sh

-#!/bin/bash
+#!/bin/sh
 
 set -e