[Tests] Add option to use 2 MQTT connections to run-performance-tests.sh
[Tests] Add option to use 2 MQTT connections to run-performance-tests.sh

Change-Id: I2f9d224df8e7c140883b3a7c13d63d394c106d27

bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr,bmwcarit/joynr