AMBARI-24879. kAdmin principal name is set on the GUI when enabling Kerberos with MIT KDC using a new variable replacement function

[smolnar82]

What changes were proposed in this pull request?

The kadmin service principal name should be configurable for MIT KDC interactions. The current process assumes the kadmin service principal is kadmin/FQDN_KADMIN_HOST, but this could be different on some installations. For example, kadmin/admin.

A new kerberos-env property should be added to allow a user to change the kadmin principal name - kerberos-env/kadmin_principal_name

The default value for the new property should be kadmin/${admin_server_host|stripPort()}. To be able to do this, we have to create a new variable replacement function. For example, stripPort.

Note: related stack change is going to be submitted separately.

How was this patch tested?

Executing JUnit tests locally in ambari-server:

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 26:12 min
[INFO] Finished at: 2018-11-12T16:43:44+01:00
[INFO] Final Memory: 163M/1033M
[INFO] ------------------------------------------------------------------------

In addition to this I did an E2E testing within my vagrant environment where Kerberos was enabled using the new property (leave as the default and changing it to a custom value).

[asfgit]

Refer to this link for build results (access rights to CI server needed):
https://builds.apache.org/job/Ambari-Github-PullRequest-Builder/4508/
Test PASSed.