epicsEventDestroy errors when exiting IOCs with model-1 drivers

[kmpeters]

Soft IOCs with model-1 motor drivers don't (always?) exit cleanly. The following error occurs and a ctrl+c is necessary to kill the IOC.

epics> exit
epicsEventDestroy: pthread_mutex_destroy failed: Device or resource busy

The original discussion of the issue can be found here: https://github.com/epics-motor/motorNewport/issues/13