restapi: Return error in replace-brick

Replace brick rest api is no longer supported in the
underlying glusterfs. Hence changing the rest api
to throw an error advising user to use migrate and
add new brick instead

Change-Id: I72cf2f62c049a0d515ec1f3fde14155b63b9738f
Bug-Url: https://bugzilla.redhat.com/923196
Signed-off-by: Sahina Bose <sabose@redhat.com>