Dan Williams authored Oct 22, 2015 and Thomas Haller committed Nov 18, 2015

Modems often don't expose all the required properties until they have
been unlocked, and that includes the IP types supported by the modem.

With an autoconnect WWAN connection where the SIM requires a PIN, there
were two problems:

1) the PIN is a secret and we don't have it until it's explicitly requested
during the activation process, so we cannot gate GSM connection availability
on whether a PIN is present since this happens long before we request secrets

2) when the modem is locked it may not report the supported IP types, which
caused an auto-activation to fail early becuase IP compatibility is checked
before the PIN is sent to the modem

Rework connection activation flow into a series of concrete steps, where the
PIN is sent to the modem if required, and only after the modem is actually
unlocked does the connection proceed.  This does mean that any connection
marked 'autoconnect' can theoretically enable a PIN-locked modem even if
the connection has no PIN defined, but there's no good way around that.
NetworkManager would activate the connection