many scanner improvements

+ added sudo access check at the very begging of the scanner,
  because some of the configured checks/commands require it
===> This includes a check for requiretty being disabled,
     including a special error message.

+ added check for ntpd service

+ added check for iptables firewall
===> I realize that the long one-line script is hard to read! Sorry about that.
     I added a backlog task to change the configuration format to allow
     multi-line check commands, so that more complex check commands
     (e.g., short scripts) are easy to add and read.

+ removed usage of grep -P

+ fixed the ValidNodeName check to report results for the correct node,
  by checking the actual hostname -s output on each node
  rather than the --nodes parameter value

+ removed ValidClusterName and HomeDirectoryNotOnNFSDisk checks
  because they may cause confusion;
  it's best to restrict these checks to the trafodion_setup script

+ removed implicit assumption that string compare will always be done
  for (eq, ne) and integer compare will always be done for (lt, le, ge, gt)

+ fixed summary output format to be less confusing

+ removed default for the --nodes parameter; this is now a required parameter,
  just like in the trafodion_setup script

Change-Id: I96ca15f40e08c1a702b0c2754d1e47da3d03f96a