Disable canonicalization in ccselect tests

DNS canonicalization can interfere with the fallback tests by changing
"localhost" to have multiple components, or (less likely) changing the
parent domain of foo.krbtest.com or foo.krbtest2.com.

src/tests/gssapi/t_ccselect.py

@@ -24,10 +24,13 @@
 
 from k5test import *
 
-# Create two independent realms (no cross-realm TGTs).
-r1 = K5Realm(create_user=False)
-r2 = K5Realm(create_user=False, realm='KRBTEST2.COM', portbase=62000,
-             testdir=os.path.join(r1.testdir, 'r2'))
+# Create two independent realms (no cross-realm TGTs).  For the
+# fallback realm tests we need to control the precise server hostname,
+# so turn off DNS canonicalization.
+conf = {'libdefaults': {'dns_canonicalize_hostname': 'false'}}
+r1 = K5Realm(create_user=False, krb5_conf=conf)
+r2 = K5Realm(create_user=False, krb5_conf=conf, realm='KRBTEST2.COM',
+             portbase=62000, testdir=os.path.join(r1.testdir, 'r2'))
 
 host1 = 'p:' + r1.host_princ
 host2 = 'p:' + r2.host_princ