gnomeos-install: use /bin/bash, not /bin/sh

This scripts use bashisms, so use /bin/bash as the interpreter until
they are un-bashified.

gnomeos/gnomeos-install.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # -*- indent-tabs-mode: nil; -*-
 # Install OSTree to system
 #

gnomeos/gnomeos-setup.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # -*- indent-tabs-mode: nil; -*-
 # Set up ostree directory
 #