Previously Delta Chat tried all DNS resolution results
in sequence until TCP connection is established successfully,
then tried to establish TLS on top of the TCP connection.
If establishing TLS fails, the whole
connection establishment procedure failed
without trying next DNS resolution results.
In particular, in a scenario
where DNS returns incorrect result
pointing e.g. to a server
that listens on the TCP port
but does not have correpsponding TLS certificate,
Delta Chat now will fall back to the cached result
and connect successfully.