To follow latest naming conventions, rename src/util/authhelper.[ch]
to src/util/virauth.[ch].

* src/util/authhelper.[ch]: Rename to src/util/virauth.[ch]
* src/esx/esx_driver.c, src/hyperv/hyperv_driver.c,
  src/phyp/phyp_driver.c, src/xenapi/xenapi_driver.c: Update
  for renamed include files
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>