[pulsar-broker] fix broken custom auth-provider that uses authenticationData (#5462)

Fix broken custom auth-provider that uses authenticationData

pulsar-broker/src/main/java/org/apache/pulsar/broker/service/ServerCnx.java

@@ -555,6 +555,7 @@ public class ServerCnx extends PulsarHandler {
                 sslSession);
 
             authState = authenticationProvider.newAuthState(clientData, remoteAddress, sslSession);
+            authenticationData = authState.getAuthDataSource();
             doAuthentication(clientData, clientProtocolVersion, clientVersion);
         } catch (Exception e) {
             String msg = "Unable to authenticate";