Currently, it is not possible to add a Cache Container using the admin console, cause the form is missing a required attribute 'cache-container':

JBAS014612: Operation ("add") failed - address: ([
("subsystem" => "infinispan"),
("cache-container" => "fff")
]): java.util.NoSuchElementException: No child 'default-cache' exists

according to AS7-3488 : it seems that default-cache attribute will no longer be required, so this will most likely work again in the future.
UPDATE in the latest snapshot of 2nd February, it seems it already works again

However, still there should be a form element to input a value for this attribute, it seems like it is not configurable at all (using the console) for the time being.