Nodes are restarted and reconnected as part of the test. Afterwards
`sync_blocks` is called immediately on the nodes. `sync_blocks`
first checks that all the included nodes have at least one
connection. Since adding a connection is usually happening in a
thread, sometimes nodes could run into this check before the
connection was fully established so that it would fail the entire
test.
This fix uses the `connect_nodes` helper to make the connection the
nodes. `connect_nodes` has a wait for the connection built into it.
