[DEFRA SD] Update redirection date
[DEFRA SD] Set special redirect strategy

This will mean the site dashboard reflects reality better. Transition will
automatically ignore it when they point the domain at us.
Merge pull request #901 from alphagov/defra_sd_are_special

DEFRA SD are special
Shift directgov_campaigns to be managed by transition, resolving conflicts in popular tests

Conflicts:
	data/transition-sites/directgov_campaigns.yml