[reSIProcate] Purging expired registrations

[Daniel Pocock <daniel@xxxxxxxxxxxxxxxxxxxxx>]

I notice the following code in InMemoryRegistrationDatabase.cxx, 
getContacts() is similar, it appears that the aor and/or contacts are 
returned without checking for expiry. 

I am happy to write patches for InMemoryRegistrationDatabase to purge 
the expired registrations whenever the relevent aor is queried.

Furthermore, if a class implementing RegistrationPersistenceManager is 
modified to purge expired registrations in this way, will it need to 
initiate (possibly through the stack) some callback to the 
ServerRegistrationHandler?

bool
InMemoryRegistrationDatabase::aorIsRegistered(const Uri& aor)
{
 database_map_t::iterator i;

 Lock g(mDatabaseMutex);
 i = mDatabase.find(aor);
 if (i == mDatabase.end() || i->second == 0)
 {
   return false;
 }
 return true;
}