Uninitialized memory in CBroker::RegisterModule

```
/home/michael/freedm/Broker/src/CBroker.cpp:222:27: warning: variable 'exists' is used uninitialized whenever
      'for' loop exits because its condition is false [-Wsometimes-uninitialized]
    for(unsigned int i=0; i < m_modules.size(); i++)
                          ^~~~~~~~~~~~~~~~~~~~
/home/michael/freedm/Broker/src/CBroker.cpp:230:9: note: uninitialized use occurs here
    if(!exists)
        ^~~~~~
/home/michael/freedm/Broker/src/CBroker.cpp:222:27: note: remove the condition if it is always true
    for(unsigned int i=0; i < m_modules.size(); i++)
                          ^~~~~~~~~~~~~~~~~~~~
/home/michael/freedm/Broker/src/CBroker.cpp:221:16: note: initialize the variable 'exists' to silence this warning
    bool exists;
               ^
                = false
```