oceani: mark code that doesn't need testing.

oceani: mark code that doesn't need testing.

Some code is included to check and report impossible
conditions.  Failure to exercise this code shouldn't
be seen as a failure of test coverage.
So mark such code as //NOTEST and exclude it
from statistics.

This brings test coverage up to 93%

Signed-off-by: NeilBrown <neil@brown.name>