Key store should not automatically be used if no keys specified

[arthurbarr]

If you specify keys in /etc/mqm/pki/keys and certificates in /etc/mqm/pki/trust, then these get automatically picked up, and runmqserver will create the MQ key database. It also sets this as the active key database (SSLKEYR) on the queue manager. This should not be the case if the key database would be empty. This is to allow people to supply their own key database, instead of the decomposed key/cert files.