load lload unload lunload: Tweak suppression of error messages

load lload unload lunload: Tweak suppression of error messages

These commands suppress some error messages when ships, planes or land
units involved aren't explicitly selected by UID.  Without this, a
command like "unload plane 80 *" would complain about every plane not
on ship#80.

Correct a few issues with this error suppression:

1. We don't suppress the error when we can't load/unload a ship or
land unit because it's on the trading block.  Do suppress it.

2. We suppress the error message when we can't load/unload due to
foreign sector ownership in all but one places.  Fix that place.

3. Messages about explicitly selected planes and land units to load
are still suppressed when the carrier isn't selected explicitly.
Change this to suppress regardless of the carrier.

3. We suppress the error when a carrier has no room.  Don't, because
it's a potentially confusing silent failure.

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