Store Principal Name Index in the Hazelcast Session delta

Issue gh-1801

Author: s-londono

spring-session-hazelcast/hazelcast4/src/main/java/org/springframework/session/hazelcast/Hazelcast4IndexedSessionRepository.java

@@ -441,6 +441,7 @@ public void setAttribute(String attributeName, Object attributeValue) {
 						.resolveIndexesFor(this);
 				String principal = (attributeValue != null) ? indexes.get(PRINCIPAL_NAME_INDEX_NAME) : null;
 				this.delegate.setAttribute(PRINCIPAL_NAME_INDEX_NAME, principal);
+				this.delta.put(PRINCIPAL_NAME_INDEX_NAME, principal);
 			}
 			flushImmediateIfNecessary();
 		}