This class relies heavily on Hadoop API to
- Check need for secure login in Hadoop
- Parse and load .xml configuration file
- Do a Kerberos login with a kaytab file
- convert _HOST in Kerberos principal to current hostname
It uses Hadoop Configuration to parse XML configuration files.
It uses Hadoop Security to modify principal and perform the login.
The major limitation in this class is its dependency on Hadoop. If Hadoop
security is off, no login will be performed regardless of connector being
used.