Reduced warn log entry without stacktrace for startup exceptions

Issue: SPR-13663

spring-context/src/main/java/org/springframework/context/support/AbstractApplicationContext.java

@@ -541,7 +541,10 @@ public abstract class AbstractApplicationContext extends DefaultResourceLoader
 			}
 
 			catch (BeansException ex) {
-				logger.warn("Exception encountered during context initialization - cancelling refresh attempt", ex);
+				if (logger.isWarnEnabled()) {
+					logger.warn("Exception encountered during context initialization - " +
+							"cancelling refresh attempt: " + ex);
+				}
 
 				// Destroy already created singletons to avoid dangling resources.
 				destroyBeans();