up_client_get_devices was deprecated in libupower 0.99.8. Migrate to up_client_get_devices2 when it's available on all the bots.

Our current Linux fleet runs on a mix of Linux releases:

• Prod: Focal with libupower 0.99.11 which deprecates up_client_get_devices and includes up_client_get_devices2.
• Trybots: Bionic with libupower 0.99.7 which does not deprecate up_client_get_devices and does not include up_client_get_devices2.

Until the bots are all migrated, we make the call to up_client_get_devices and ignore deprecations. Once the migration has completed, I'll update the call to the new one.