Fix issue when SELinux is enabled
Fix issue when SELinux is enabled

Remounting the directory as read-only appears to make the chroot
believe that SELinux is disabled.

dnschneid/crouton,nromsdahl/crouton,dnschneid/crouton,dnschneid/crouton,nromsdahl/crouton,dnschneid/crouton,jamgregory/crouton,nromsdahl/crouton,dnschneid/crouton,jamgregory/crouton,jamgregory/crouton,jamgregory/crouton,nromsdahl/crouton,dnschneid/crouton,nromsdahl/crouton,jamgregory/crouton,jamgregory/crouton,nromsdahl/crouton