Improve checks during Trafodion Kerberos Installation

Add checks for security configuration issues at the same time other config problems are checked (traf_config_check). Today problems are not discovered until late in the process. When problems are found, it is not always easy to figure out the issue. Checks to include:

-> valid KDC server and LDAP server
-> valid KDC admin user and password
-> LDAP user to be associated with database user ROOT is valid

Also, remove the hard coded location for the Hadoop's core-site.xml file. Some installations may not be using the standard location.