LP:682967 - auto-increment-offset shouldn't be allowed to be greater than auto-increment-increment

Apart from both of these variables not allowed to be 0, auto-increment-offset should not be allowed to be greater than auto-increment-increment as that would by definition create an invalid scenario.

For startup, this could be checked after the config/cmdline params are all processed - this to prevent chucking an error in case they're specified with offset first and increment second.
For live changes, it could be checked on the spot - although I'd question the sense/need of changing such params live.