Improve TAC status report and killing phase in tango_wca script

Before, at least on Ubuntu 16.04, "tango_wca start" and "tango_wca status" were complaining that TAC server was not started, even though it was actually started. tango_wca script was not able to stop the TAC server on Ubuntu 16.04. Improve tango and tango_wca scripts to limit the risk to kill another process containing Database in its executable name.