OpenStack installation instructions from openstack.org assume 3 node architecture therefore and the biggest problems that can be encountered while performing AIO (all-in-one) installation are with Swift.
In order to perform AIO installation for Swift the following instructions must be followed:
With some modifications according to normal installation instructions of Juno on Ubuntu (just use common sense to modify e.g. IPs accordingly, add keystone authentication as it is missing in AIO). After this installation command swift stat works properly.
If any swift related process does not start then it needs to be ensured that e.g. log directories/files have owner set to swift:swift.