My use case for this feature is to exclude network devices that use
the cdc_ether driver. These USB network interfaces often cause all sorts
of issues. For example, some models have the same hardcoded MAC address,
which breaks inspection.
Currently, to exclude a certain device, a hardware manager must override
the entire listing function (in my case, list_interfaces). Not only is
it tedious, but it also requires constantly updating the hardware
managers to match the implementation in GenericHardware. Realistically,
it will cause hardware manager authors to inherit GenericHardware, which
is the opposite of how hardware managers should be written.
Note that the node-level skip list only affects root device selection
and cleaning for block devices. This feature affects everything that
uses list_block_devices and is applied before the node-level skip list.
This change adds a new hardware manager call filter_device. For each
network, block or USB device, it allows a hardware manager to do either
of four things:
1. Delegate the decision to a lower level hardware manager by raising
 IncompatibleHardwareMethodError
2. Remove the device by returning None
3. Change the device by returning a modified instance
4. Return the device unchanged to keep it in the listing.
Note that I'm removing debug logging when IncompatibleHardwareMethodError
is raised. Not only the log message is incorrect (the error does not
necessarily mean that the method is not implemented at all), it already
noticeable space in the logs, and with this change will become very
noisy.
Change-Id: I5437343af6c6157882bcf0600dd89bd20478c948
Signed-off-by: Dmitry Tantsur <dtantsur@protonmail.com>