GEOM: Minor polishing in geom_event.

• Remove timeouts from msleep()'s. Those should always be woken up.
• Move wakeup() under the lock to not call on possibly freed pointer.
• Remove some dead code.

MFC after: 2 weeks

(cherry picked from commit f4bf48c25c3a8de3fbfd49b45b2d59026df13a6a)