The implementation of security driver callbacks often needs
to access the security driver object. Currently only a handful
of callbacks include the driver object as a parameter. Later
patches require this is many more places.

* src/qemu/qemu_driver.c: Pass in the security driver object
  to all callbacks
* src/qemu/qemu_security_dac.c, src/qemu/qemu_security_stacked.c,
  src/security/security_apparmor.c, src/security/security_driver.h,
  src/security/security_selinux.c: Add a virSecurityDriverPtr
  param to all security callbacks