Summary:
Jenkins would hang at a random time while running all the tests.
The reason for that is a bug in skiplist implementation.
Skiplist method find_or_larger was never ending and would continuously stay in the while loop because the next node (with the queried value) onto which it would try to jump would be marked as deleted and that would stop it from jumping on it, or ending on that node.
Reviewers: buda, teon.banek, mislav.bradac
Reviewed By: buda
Subscribers: pullbot
Differential Revision: https://phabricator.memgraph.io/D334
