Since the mainline kernel is now at v4.9-rc5, it might be worth giving it a test. If it fixes the boot slowness, time would be better spent looking for the fix, versus continuing a search on what broke it.
V4.9-rc5 can be downloaded from: http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.9-rc5/
Since the mainline kernel is now at v4.9-rc5, it might be worth giving it a test. If it fixes the boot slowness, time would be better spent looking for the fix, versus continuing a search on what broke it.
V4.9-rc5 can be downloaded from: kernel. ubuntu. com/~kernel- ppa/mainline/ v4.9-rc5/
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