The "mesos-health-check" binary is not used anymore.

MESOS-5727 and MESOS-5954 refactored the health check code into the HealthChecker library, hence the "mesos-health-check" binary became unused.

While the command and docker executors could just use the library to avoid the subprocess complexity, we may want to consider keeping a binary version that ships with the installation, because the intention of the binary was to allow other executors to re-use our implementation. On the other side, this binary is ill suited to this since it uses libprocess message passing, so if we do not have code that requires the binary it seems ok to remove it for now. Custom executors may use the HealthChecker library directly, it is not much more complex than using the binary.