Recommited with post-review fixes


server-tools/instance-manager/instance.cc:
  fix behaviour of monitoring routines: they should not  rely on the fact that instance object
  which was used when the instances started exists at stop(). Instead routines should save the
  name of the instance and look for it in the instance_map when needed.
server-tools/instance-manager/instance.h:
  new functions declared. functions, which were converted to static removed from the class.
server-tools/instance-manager/instance_options.cc:
  fix valgrind warning