Accepting a percentage for min_speed

[Nobuto Murata]

Currently "min_speed" config option only accepts an absolute value of bandwidth.
https://charmhub.io/magpie/configure#min_speed
> min_speed | int
>
> Minimum transfer speed in mbit/s required to pass the test. 0 disables.

It would be nice if it can accept a percentage like 80% or 90% of the link speed so it would be easier to use the option in a mixed link speed environment (1Gbps + 10Gbps or 10Gbps + 40Gbps).

[Samuel Allan (samuelallan)]

patch: https://review.opendev.org/c/openstack/charm-magpie/+/845084

[Nobuto Murata (nobuto)]

Subscribing ~field-medium.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/charm-magpie/+/845084
Committed: https://opendev.org/openstack/charm-magpie/commit/720b6357264ae1fe493456304fe986e95b9ca131
Submitter: "Zuul (22348)"
Branch: master

commit 720b6357264ae1fe493456304fe986e95b9ca131
Author: Samuel Walladge <email address hidden>
Date: Wed Jun 8 15:36:49 2022 +0930

    Add support for min_speed percentage of link speed

    This can be useful for environments with mixed link speeds.

    Example:

    ```
    juju config magpie min_speed=80%
    ```

    Further note on behaviour: if a percentage min_speed is set,
    and the link is virtual or otherwise returns a negative speed,
    magpie will fail the speed check.
    (percentage of an undefined value is still undefined)

    Closes-Bug: #1977784

    Change-Id: I1fa5d38a4da26ca38e98350d1a1625184dff2363