Fix null pointer dereference and assertion failure conditions that
could cause a denial of service.

https://github.com/krb5/krb5/commit/c25278d502cb3d8930fd50c49ff1d506e69f045e
Commit By: tlyu
Revision: 25370
Changed Files:
U   branches/krb5-1-8/src/plugins/kdb/db2/lockout.c
U   branches/krb5-1-8/src/plugins/kdb/ldap/libkdb_ldap/ldap_principal2.c
U   branches/krb5-1-8/src/plugins/kdb/ldap/libkdb_ldap/lockout.c