Stop any mosquitto instance which may be still running from previous runs

Signed-off-by: Juergen Kosel <juergen.kosel@softing.com>

travis-install.sh

@@ -3,6 +3,8 @@
 if [ "$TRAVIS_OS_NAME" == "linux" ]; then
 	pwd
 	sudo service mosquitto stop
+	# Stop any mosquitto instance which may be still running from previous runs
+	killall mosquitto
 	mosquitto -h
 	mosquitto -c test/tls-testing/mosquitto.conf &
 fi