Trim the 'repeat' test.

By cutting down the number of TESLA instances per automaton class, we significantly improve on run time and debug output while still triggering the mysterious pthread assertion failure on FreeBSD.
tesla_class_reset should not unlock a tesla_class.

tesla_class_reset() should only be called with a tesla_class that is already locked (for classes that require synchronisation); unlocking it is the responsibility of the code that took out the lock. With the current implementation, tesla_update_state() does a double release whenever it resets a class.

It's unfortunate that neither the Mac OS X nor the Linux pthreads implementations caught this problem! Only FreeBSD's implementation returned EPERM when releasing an unheld lock (double release).