Don't log until we know we have an affiliation

Fixes #73 
Minor point, but it's generally encouraged to stick a guard around log.debug statements that do any work (i.e. string concatenation) as the concatenation will happen even if debug logging is turned off. e.g.,
```java
if(LOGGER.isDebugEnabled()) {
    LOGGER.debug(userBareJID + " affiliation: " + affiliation.getType().toString());
}
```