Fixed #20936: When logging out/ending a session, don't create a new, empty session

Previously, when logging out, the existing session is overwritten by a
new sessionid instead of deleting the session all together.

This behavior adds overhead by creating a new session record in
whichever backend being used, db, cache, etc.

This extra session is unnecessary at the time since no session data
is meant to be preserved when explicitly logging out.