switch_to_interface() becomes the common place where
self.interface is set; therefore self.interface is not None
precisely when self.default_server is connected. Previously some
places required it to be connected and some didn't. Also an
interface change now sends the 'updated' notification
consistently - previously some did and some didn't.
Have network_start() call start_interfaces() - this also means
network restarts now do this.
Fix apparent off-by-one in start_interfaces()
Prefer to use safer self.is_connected() as it checks interface
is not None.
Using common code gives small observable changes in behaviour:
- slightly different print_error() messages
- network restarts now enter status 'connecting' which they
didn't before, which seems correct
- status 'connecting' is done with set_status() rather than
simply assigning the status, which seems more correct. Now
that the response_queue is available in the constructor this
works; it used to fail with 'response_queue is not defined'
This is somewhat cleaner as the proxy's pipe and network setup
was awkwardly interleaved. It also means network's constructor
is free to use both; currently some code is working around the
fact that the response queue doesn't exist in the constructor.
We store it in the config object instead of in the blockchain object.
The blockchain object now refers to its config, and calls refresh_height() to update it.
The network objects also refer to the config rather than the blockchain.
This is the first of many small steps to untangle the verifier from stored state and so
permit the history tab to work in offline mode. The refactoring will simultaneously clean
up a lot of accumulated cruft.