726401: Systems page - needs better error behavior when tomcat6 is not running

ECONNREFUSED error shows up when tomcat6 is not running.So we handled that exception by throwing user-friendly error.In order for it to work we had to handle exception in http_resource.rb and defined a custom exception - ConnectionRefusedException in errors.rb.
Merge pull request #2412 from pgodhani/tomcat6

726401: Systems page - needs better error behavior when tomcat6 is not r...