No prefix suggestion of special and media namespace on special pages

No prefix suggestion of special and media namespace on special pages

As mention in comments of I71f77c3001a12d75b901807c20115cead9c64e93 the
added prefix suggestion can get called recursive.
Avoid this by disable prefix suggestion for media and special namespace,
because a special page cannot be used on that special pages.

Follows I71f77c3001a12d75b901807c20115cead9c64e93

Change-Id: I8978e3bd0783f62bc25b32a0fdaa90361abefcf3