opencv: Fix metapkg dependencies for opencv-java and opencv-locales

The opencv-java is not always generated so we ought to include it,
only if it is available. The opencv-locales is not available and ought
to be skipped.

Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Armin Kuster <akuster808@gmail.com>