[CI] KerberosAuthenticationIT fails in CI

[danielmitterdorfer]

Build failure link: https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+6.4+multijob-unix-compatibility/os=centos/7/console

./gradlew :x-pack:qa:kerberos-tests:integTestRunner \
  -Dtests.seed=96A4AD9F42092F61 \
  -Dtests.class=org.elasticsearch.xpack.security.authc.kerberos.KerberosAuthenticationIT \
  -Dtests.security.manager=true \
  -Dtests.locale=und \
  -Dtests.timezone=Etc/GMT-11

testLoginByKeytab and testLoginByUsernamePassword fail with:

KrbException: Identifier doesn't match expected value (906)

and also

KrbException: Server not found in Kerberos database (7) - LOOKING_UP_SERVER

This issue does not reproduce locally.

[elasticmachine]

Pinging @elastic/es-security

[danielmitterdorfer]

The tests are muted now on 6.4, 6.x and master (see above for commit ids).

[danielmitterdorfer]

Another failure happened in https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+6.x+multijob-unix-compatibility/os=centos/1214/console.

[jaymode]

This is failing due to the use of [::1] as the address in the rest client and the fact that the test always expects the http address to be localhost. I opened #32514 to address this