Remove usage of beanstalk from teuthology

Remove usage of beanstalk from teuthology

The following changes support the removal of Beanstalk from Teuthology.
In place of Beanstalk, we will now be using Paddles for queue management in Teuthology.
This PR has the corresponding changes for the paddles PR: https://github.com/ceph/paddles/pull/94/files.

The changes include:
1. Removing all beanstalk related code
2. Teuthology scheduler and dispatcher using Paddles queue for scheduling and dispatching jobs
3. Adding support for Paddles queue management
4. Additional functionality of being able to change the priority of Teuthology jobs in the queued state in the teuthology-queue command

Signed-off-by: Aishwarya Mathuria <amathuri@redhat.com>