SASL server fails when FQDN is greater than 63 characters long in Kudu RPC

In the current Kudu RPC implementation, we don't explicitly pass the host's FQDN into the SASL library. Due to an upstream SASL bug (https://github.com/cyrusimap/cyrus-sasl/issues/583) the FQDN gets truncated when trying to determine the server's principal, in the case that the server's fQDN is longer than 64 characters.

This results in startup failures where the preflight checks fail due to not finding the appropriate keytab entry (after searching for a truncated host name)

To work around this, we should use our own code to compute the FQDN.

Kudu is making the changes in it's own implementation here:

https://issues.apache.org/jira/browse/KUDU-2989, we should do the same.