Implement locking for tasks to prevent race conditions

[sjmf]

Problem:

Multiple instances of the same task can be served to celery. For example, loadParameters is a long running task. If it is kicked off in the interface multiple times, or scheduled too closely together, another task should not start to run while the existing one is running.

Solution:
A locking mechanism will need to be implemented in the application to stop tasks from colliding in this way. For example, http://loose-bits.com/2010/10/distributed-task-locking-in-celery.html and https://docs.celeryq.dev/en/latest/tutorials/task-cookbook.html#ensuring-a-task-is-only-executed-one-at-a-time