nvme: Inject artificial failure on reset

[imp]

Summary

Add a sysctl to artificially fail the reset to test the failure to reset
hardware code path.

[mav]

It is so specific code debugging case, that I see no much sense to add the tunable for it, rather then just do it once when the code is modified.

[imp]

In D28584#639918, @mav wrote:

It is so specific code debugging case, that I see no much sense to add the tunable for it, rather then just do it once when the code is modified.

I was rather hoping to have automated testing use this... That's why I opted to submit this for review...

However, I can hold off committing it until that automated testing is in place.