Callable can outrun periodicity of POSIX timer

[mossmaurice]

Required information

Operating system:
Ubuntu 18.04 LTS

Compiler version:
GCC 7.5.0

Observed result or behaviour:
If callable is taking more time than periodicity then OS creates more and more threads are created that hang in the mutex (e.g. every 10ms and callable takes 15ms)

Expected result or behaviour:
Call std::terminate or in debug mode just return from the newly created thread.

Conditions where it occurred / Performed steps:
Start ./RouDi, attach GDB in nostop mode and stop a RouDi thread, leaving all other threads e.g. MqThread running

[mossmaurice]

Closing this issue, as it will be addressed with #167