Upgrade to MQTT Paho 1.2.2

- fix mock tests for internal client changes
- reduce stop wait for completion time

**cherry-pick to 5.2.x**

* Remove stack trace from test and convert to assertJ

build.gradle

@@ -82,7 +82,7 @@ ext {
 	mockitoVersion = '3.2.4'
 	mongoDriverVersion = '4.0.0-beta1'
 	mysqlVersion = '8.0.19'
-	pahoMqttClientVersion = '1.2.0'
+	pahoMqttClientVersion = '1.2.2'
 	postgresVersion = '42.2.10'
 	reactorVersion = 'Dysprosium-SR4'
 	resilience4jVersion = '1.3.1'