LUDOC-11 debug: add went_back_in_time label

LUDOC-11 debug: add went_back_in_time label

Add a section label for the "went back in time" error message,
so that it can more easily be referenced by an error message
in the code (formerly a link to a bugzilla ticket).

Improve the description of the problem and reformat the text
to fit within 80 columns.

Signed-off-by: Andreas Dilger <adilger@dilger.ca>
Change-Id: I612cbd090cd695272009754364be53f65c3ebbe5
Reviewed-on: https://review.whamcloud.com/35954
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Joseph Gmitter <jgmitter@whamcloud.com>