Adjust test-case for log4j2 custom fields

Test numerical valued custom field as well.

Signed-off-by: Karsten Schnitter <k.schnitter@sap.com>

Author: KarstenSchnitter

cf-java-logging-support-log4j2/src/test/java/com/sap/hcp/cf/log4j2/layout/suppliers/EventContextFieldSupplierTest.java

@@ -53,12 +53,12 @@ public void customFields() throws Exception {
         Object[] arguments = new Object[] { //
                                             new Object(), //
                                             CustomField.customField("key", "value"), //
-                                            CustomField.customField("this", "that") };
+                                            CustomField.customField("this", Double.valueOf(123.456d)) };
         when(event.getMessage().getParameters()).thenReturn(arguments);
 
         Map<String, Object> fields = fieldSupplier.map(event);
         assertThat(fields, hasEntry("key", "value"));
-        assertThat(fields, hasEntry("this", "that"));
+        assertThat(fields, hasEntry("this", Double.valueOf(123.456d)));
     }
 
     @Test