If a device is already activated, queue the new activation to allow
the transition through the DEACTIVATING state.
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Also remove the "HACK" bits in nm_device_deactivate(). This hack was
added on 2007-09-25 in commit 9c2848d. At the time, with user settings
services, if a client created a connection and requested that NM
activate it, NM may not have read the connection from the client over
D-Bus yet. So NM created a "deferred" activation request which waited
until the connection was read from the client, and then began activation.
The Policy watched for device state changes and other events (like
it does now) and activated a new device if the old one was no longer
valid. It specifically checked for deferred activations and then
did nothing. However, when the client's connection was read, then
nm-device.c cleared the deferred activation bit, leading to a short
period of time where the device was in DISCONNECTED state but there
was no deferred activation, because the device only changes state to
PREPARE from the idle handler for stage1. If other events happened
during this time, the policy would tear down the device that was
about to be activated. This early state transition to PREPARE
worked around that.
We need to remove it now though, because (a) the reason for its
existence is no longer valid, and (b) _device_activate() may now
be called from inside nm_device_state_changed() and thus it cannot
change to a new state inside the function.