(#7841) Always read SELinux module header as little endian

These are always little endian, but are currently being read as native
byte order, which obviously causes failures.
Merge remote-tracking branch 'nicklewis/aix-7841-selinux-little-endian' into aix

* nicklewis/aix-7841-selinux-little-endian:
  (#7841) Always read SELinux module header as little endian