Support on-boot configuration changes

[ikeydoherty]

Case 1 (OEM):

Expected:

• OS installed using DISCRETE mode, only a single NVIDIA GPU exists
• OS rebooted, firmware set to HYBRID
• LDM should evaluate the configuration change to support HYBRID mode

Reality:

• User is left with "unbootable" system because X.Org won't work

Case 2 (User):

Expected

• User installs LTS kernel and NVIDIA driver, kernel + driver works great
• User installs CURRENT kernel WITHOUT new NVIDIA driver, reboots
• LDM should run and detect an invalidated configuration, and force MESA.

Reality

• User is left with "unbootable" system because X/GL links set for NVIDIA, nvidia.ko not loaded

Case 3 (User):

Expected:

• OS installed with hybrid GPU + LightDM
• User switches display manager to GDM and reboots
• LDM should re-evaluate configuration change to "fix" GDM and "unfix" LightDM

Reality:

• GDM isn't configured for HYBRID, session fails to start on dGPU