update/ship: Don't let stopped sectors repair foreign ships

update/ship: Don't let stopped sectors repair foreign ships

Stopping a sector disables repairs of own ships completely.  Foreign
ships, however, repair just fine, consuming the sector's materials
and, if it's a harbor, its available work.

Disable repair of all ships in stopped sectors.  This is consistent
with plane and land unit repair.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>