Code review comment for lp://qastaging/~alan-griffiths/mir/frig-1283085

(1) This sounds like a hack, should we be concerned?
   25 + // sleeping between calls to fake_devices hides race conditions
The sleep call already exists, so it's functionally no worse. Only the new comment could concern the reader.

(2) It's probably better practice to keep "<" instead of "!=" in loops like this:
   for (int i = 0; i != device_change_count; ++i)
Because that protects you from potential changes to i's initial conditions or increment.

Although if this fixes the bug then neither of those issues are worth blocking on.