Fix bug with setting the nvidia.com/vgpu.config.state label

[cdesiniotis]

Before this change, the state label would incorrectly have a value of 'success' even if the vgpu-device-manager failed to apply a particular configuration.

Before:

time="2023-12-22T18:31:50Z" level=fatal msg="error getting vGPU config: error getting all vGPU devices: unable to read MDEV devices directory: open /sys/bus/mdev/devices: no such file or directory"
time="2023-12-22T18:31:50Z" level=info msg="Changing the 'nvidia.com/vgpu.config.state' node label to 'success'"
time="2023-12-22T18:31:50Z" level=error msg="ERROR: unable to apply config 'A10-8Q': exit status 1"
time="2023-12-22T18:31:50Z" level=info msg="Waiting for change to 'nvidia.com/vgpu.config' label"

After:

time="2023-12-22T18:44:15Z" level=fatal msg="error getting vGPU config: error getting all vGPU devices: unable to read MDEV devices directory: open /sys/bus/mdev/devices: no such file or directory"
time="2023-12-22T18:44:15Z" level=error msg="Failed to apply vGPU config: unable to apply config 'A10-8Q': exit status 1"
time="2023-12-22T18:44:15Z" level=info msg=""Setting node label: nvidia.com/vgpu.config.state=failed"
time="2023-12-22T18:44:15Z" level=info msg="Waiting for change to 'nvidia.com/vgpu.config' label"