[C++] shutdown LibJoynrMessageRouter when destructing LibJoynrRuntime
[C++] shutdown LibJoynrMessageRouter when destructing LibJoynrRuntime

* shutdown LibJoynrMessageRouter in order to avoid cyclic
  dependency of shared pointer preventing destruction of
  objects (SubscriptionManager) leading to memory leak

Change-Id: Idc34af83522eedaa3bd8b6616c45a3af7386debe

clive-jevons/joynr,bmwcarit/joynr,clive-jevons/joynr,clive-jevons/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr