graphics/*_maximum_resolution_* fails on devices using nvidia drivers

[Pierre Equoy]

graphics/*_maximum_resolution_* relies on the graphics_max_resolution.py script to check the max available resolution.

One of the things checked to compute the max resolution is if the monitor is set to "enabled"[1].

Unfortunately, it seems that nvidia drivers do not set these attributes properly, leaving them to "disabled" all the time:

https://forums.developer.nvidia.com/t/sys-class-drm-enabled-reports-disabled-for-enabled-monitors/51187

This cause the graphics/*_maximum_resolution_* to be marked as failed on systems using an nvidia GPU.

Workaround: since this is a manual job, the tester can set the outcome to "Passed", but the information shown is erroneous. Example:

--------------
The displays do not seem to be configured at their maximum resolution.
Please switch to the maximum resolution before continuing.
Current compositor: x11

Maximum resolution found for each connected monitors:
 card1-DP-5: 1920x1200 (on, connected, disabled)

Current resolution found for each connected monitors:
 DP-0 (DEL): 1920x1200 @100%
--------------

In this example, the monitor reported by the nvidia driver is marked as "disabled" even though it's being used and it works as expected.

Related to lp:1983360 (internal issue)

[1] https://github.com/canonical/checkbox/commit/f3e13eabd2370771cee45fd2e6fd3940e9f65ee4#diff-ab86fac34e9c16078c3a2bc56dbb7040d4dae4f7d4c9fdfe72f28414d6a3e82cR109-R112

[Maksim Beliaev (beliaev-maksim)]

Bug was migrated to GitHub: https://github.com/canonical/checkbox/issues/249.
Bug is no more monitored here.