deskclock: remove unused multiplayer

The current Deskclock multiplayer implementation only used the random feature and
none of the real multiplayer feature, and it lacks of a proper DocumentProvider support.
This change just returns to the default mediaplayer and resolve the random feature
externally

Change-Id: I1d721d95e9528530c86f8edbc8188167348c38c4
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>