The back-port of
HADOOP-7119 to branch-0.20-security included tests which require Kerberos infrastructure in order to run. In trunk and 0.23, these are disabled unless one enables the testKerberos maven profile. In branch-0.20-security, these tests are always run regardless, and so fail most of the time.
See this Jenkins build for an example: https://builds.apache.org/view/G-L/view/Hadoop/job/Hadoop-0.20-security/26/