Avoid referencing nonexistent AgencyId vars

In fail() and do_user_lookup_error_stanza(), we were attempting to
call staff_log() with values for FromAgencyId and ToAgencyId using
variables which did not exist.

Also, in fail() we were attempting to use those same variables in
the creation of an XML NCIP response.

The above issues would result in "Use of uninitialized value"
warnings, as well preventing use of "use strict".

This commit removes the references to the nonexistent variables,
resulting in the same log and xml output.

A future commit may provide a means for these functions to log the
FromAgencyId and ToAgencyId.

Signed-off-by: Jeff Godin <jgodin@tadl.org>