Reducing level from error to warning on block order - will be error in ARC 7. (BUGZ-3996)

The proposed fix in !1328 (merged) gives an error message in arcctl config verify although AREX starts w/o problems (at least if authgroup and mapping are in correct order). Since all blocks in this suggestion should be in an exact order, but that order is not yet in ARC 6 enforced, the message is reduced to a warning.

For ARC 7 it should again be an error, and actually prevent AREX from starting.