DDF: container_content_ddf: set safe_mode_delay > 0

DDF: container_content_ddf: set safe_mode_delay > 0

Set safe_mode_delay to something >0, otherwise all container subarrays
assembled will have safe_mode_delay=0. That will break the assumption that
meta data becomes clean after running mdadm --wait-clean.

Use the same value as in getinfo_super_ddf_bvd. It would be cleaner
to call that directly from container_content_ddf, but I need to check
possible side effects first.

Signed-off-by: Martin Wilck <mwilck@arcor.de>
Signed-off-by: NeilBrown <neilb@suse.de>