gswauth: Fix 403 being returned instead of 401

- 401(Unauthorized) is to be returned when user credentials are
  wrong where as 403(Forbidden) is to be returned when user
  credentials are correct but the user doesn't have the priveleges
  to carry out the operation.

- Also error messages displayed when using swauth-* command line
  utilities have been updated.

Change-Id: I485786896ad14d3263f4325d1857cacc93adab96
Signed-off-by: Prashanth Pai <ppai@redhat.com>
Reviewed-on: http://review.gluster.org/6336
Reviewed-by: Luis Pabon <lpabon@redhat.com>
Tested-by: Luis Pabon <lpabon@redhat.com>
Signed-off-by: Prashanth Pai <ppai@redhat.com>
Reviewed-on: http://review.gluster.org/6447
Reviewed-by: Thiago Da Silva <thiago@redhat.com>
Tested-by: Thiago Da Silva <thiago@redhat.com>