mismatch_cnt != 0, member content mismatch, but md says the mirror is good

[Michael ODonnell]

In finest NIH form we could deal with the scrubber/patrol terminology
question by inventing a new acronym.  How about "GRIDLEBYRF" for
Gratuitous Reads Intended to Detect Latent Errors Before You're Royally
Fscked ?  FWIW, back around 2003 I wrote such logic for an early release
of MD on Red Hat 9 and we called it a scrubber, though I'm not sure who
came up with that term or why...