Add support for locking the loopback block device via `flock(2)`.
The main use case for this is to prevent systemd-udevd from
proben the device while any modification is done to it. See the
systemd page, https://www.freedesktop.org/software/systemd, for
more details.
Add the corresponding tests to it.
Add a helper method that clears the fd for a given loop device but
also ensures that the loop device is not bound to the supplied fd
anymore. Check the function documentation for more information.
Add a corresponding test.
Add a `Loop.is_bound_to` helper that checks if the looback device is
bound if is so if the backing file refers to the same file as `fd`.
The latter is done by comparing the device and inode information.
Add a helper that will check if the loop devices is backed by
the file identified via the stat(2) result, i.e. the inode on
the correspoding device.
Add a correspoding test for the new helper.
Implement a `Loop.get_status` method, to get the properties of the
loop device, corresponding to LOOP_GET_STATUS64, and counterpart
to the existing `Loop.set_status` method. Use the new `get_status`
call in the `set_status` call, replacing the existing code that
does the same thing.
Add a basic test for the `get_status` method. Also fix an actual
leak, where the loop device was closed but the fd was not cleared
inside the test.
