pthread_mutex calls do not always check return code

[Dave George]

In quite a few places, the code shows:
  pthread_mutex_lock(<mutex>) or pthread_mutex_unlock(<mutex>)
The return code from these calls should be checked.

A more generic summary would be something like:
return codes from functions that return error codes should be checked.

It may be possible to use coverity or other such tool in trying to automate the more general issue.

[Dave George (d-george-b)]

I will add more notes later - but there is a checker:
coverity/6.0.2/cov-analysis/sdk/sq/return-check