Comment 0 for bug 1717151

nvidia-375.postinst not always build initramfs by default:
"
        ALTERNATIVE=$(readlink /etc/alternatives/x86_64-linux-gnu_gl_conf)
        if [ "$ALTERNATIVE" = "/usr/lib/nvidia-375/ld.so.conf" ]; then
            # Update initramfs so that the blacklist ends up in the initramfs
            if [ -x /usr/sbin/update-initramfs ]; then
                /usr/sbin/update-initramfs -u
"

it the case of user who are using intel then update driver from nvidia-375.20 to nvidia-375.82 will get screen dark after prime-select nvidia later.

syslog:
"
NVRM: loading NVIDIA UNIX x86_64 Kernel Module 375.20 Tue Nov 15 16:49:10 PST 2016 (using threaded interrupts)
......
NVRM: API mismatch: the client has the version 375.82, but
NVRM: this kernel module has the version 375.20. Please
NVRM: make sure that this kernel module and all NVIDIA driver
NVRM: components have the same version.
"

The root cause is the nvidia kernel module in initramfs not be updated in this case.

impacted issues:
LP: #1651627