Some types of audit event samples from [our documentation](https://www.elastic.co/guide/en/elasticsearch/reference/7.17/audit-event-types.html) include the port number in "origin.address", like **access_denied**:
```json
{"type":"audit", "timestamp":"2020-12-30T22:30:06,949+0200", "node.id":
"0RMNyghkQYCc_gVd1G6tZQ", "event.type":"transport", "event.action":
"access_denied", "authentication.type":"REALM", "user.name":"user1",
"user.realm":"default_native", "user.roles":["test_role"], "origin.type":
"rest", "origin.address":"[::1]:52434", "request.id":"yKOgWn2CRQCKYgZRz3phJw",
"action":"indices:admin/auto_create", "request.name":"CreateIndexRequest",
"indices":["<index-{now/d+1d}>"]}
```
but other types like **connection_denied** from this issue does not include the port:

```json
{"type":"audit", "timestamp":"2020-12-30T21:47:31,526+0200", "node.id":
"0RMNyghkQYCc_gVd1G6tZQ", "event.type":"ip_filter", "event.action":
"connection_denied", "origin.type":"rest", "origin.address":"10.10.0.20",
"transport.profile":".http", "rule":"deny 10.10.0.0/16"}
```

I think we should be consistent here and always include the port number in the "origin.address" field.
x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/audit/AuditTrailServiceTests.java
private TransportRequest request;
    private RestRequest restRequest;
    private MockLicenseState licenseState;
    private boolean isAuditingAllowed;
    @Before
    public void init() throws Exception {
        List<AuditTrail> auditTrailsBuilder = new ArrayList<>();
        for (int i = 0; i < randomIntBetween(1, 4); i++) {
            auditTrailsBuilder.add(mock(AuditTrail.class));
        }
        auditTrails = unmodifiableList(auditTrailsBuilder);
        licenseState = mock(MockLicenseState.class);
        service = new AuditTrailService(auditTrails, licenseState);
        isAuditingAllowed = randomBoolean();
        when(licenseState.isAllowed(Security.AUDITING_FEATURE)).thenReturn(isAuditingAllowed);
        token = mock(AuthenticationToken.class);
        request = mock(TransportRequest.class);
        restRequest = mock(RestRequest.class);
    }
    public void testLogWhenLicenseProhibitsAuditing() throws Exception {
        MockLogAppender mockLogAppender = new MockLogAppender();
        mockLogAppender.start();
        Logger auditTrailServiceLogger = LogManager.getLogger(AuditTrailService.class);
        Loggers.addAppender(auditTrailServiceLogger, mockLogAppender);
        when(licenseState.getOperationMode()).thenReturn(randomFrom(License.OperationMode.values()));
        if (isAuditingAllowed) {
            mockLogAppender.addExpectation(
                new MockLogAppender.UnseenEventExpectation(
                    "audit disabled because of license",
                    AuditTrailService.class.getName(),