Remove race situations that occur when removing pidfiles. Primarily each process should remove its own
pidfile, secondly it should be removed by the process that created it and _only_ if it's
certain the process is dead. Third, mysql-test-run.pl will remove the pidfile when process has been killed.
- Set state of an instance to STARTING _before_ calling instance->start()
- Check that pidfile of instance has been created before changing STARTING => STARTED
- Only remove the pidfile if IM kills an instance with SIGKILL, otherwise the instance will remove it itself


server-tools/instance-manager/guardian.cc:
  If state of an instance is STARTING, chech that the instance pidfile has been created
  before changing state to STARTED
  Set state to STARTING before calling instance->start(), it can take some time
  before it is fully started and during that time it should be in state STARTING
server-tools/instance-manager/instance.cc:
  Only remove the pid file of instance manager when a SIGKILL has 
  been performed sucessfully
server-tools/instance-manager/instance_options.cc:
  Check that fscanf returns 1 which is the number of args that should be scanned from
  the pid file