Remove stray exit in t_referral.py

Commit 1dc619624421002b1e64d3b8c7e270508381b3e6 included a stray
"exit(0)" for debugging.  Remove it.

https://github.com/krb5/krb5/commit/73e40a81df07d035d1a86b871012d022d38fb9e3
Author: Greg Hudson <ghudson@mit.edu>
Commit: 73e40a81df07d035d1a86b871012d022d38fb9e3
Branch: master
 src/tests/t_referral.py |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)