Add call to reset Logback on test class initialization.

Resolves gh-73.

spring-geode-tests/smoke-tests/logging/src/main/java/example/app/geode/logging/ApacheGeodeLoggingApplication.java

@@ -76,6 +76,8 @@ public class ApacheGeodeLoggingApplication {
 	@SuppressWarnings("unchecked")
 	private static StringAppender configureAndInitializeLoggingSystem() {
 
+		LogbackSupport.resetLogback();
+
 		LoggerContext loggerContext = LogbackSupport.requireLoggerContext();
 
 		LogbackSupport.suppressSpringBootLogbackInitialization();