The logic leading to immediate disconnect when connecting to ourself has
been first introduced by Satoshi in October 2009.
Initiating an outbound network connection currently involves the
following steps after the socket connection is established (see
`CConnman::OpenNetworkConnection` method):
1. set up node state
2. queue VERSION message
3. add new node to vector `m_nodes`
If we connect to ourself, it can happen that the sent VERSION message
(step 2) is received and processed locally *before* the node object
is added to the connection manager's `m_nodes` vector (step 3). In this
case, the self-connect remains undiscovered, as the detection doesn't
find the outbound peer in `m_nodes` yet (see `CConnman::CheckIncomingNonce`).
Fix this by swapping the order of 2. and 3., by taking the `PushNodeVersion`
call out of `InitializeNode` and doing that in the `SendMessages` method
instead, which is only called for `CNode` instances in `m_nodes`.
Thanks go to vasild, mzumsande, dergoegge and sipa for suggestions on
how to fix this.
This is a backport of core#30394 and core#30362
Depends on D18452