Investigate potential race condition with watchers

cf failed test: https://github.com/netobserv/network-observability-operator/actions/runs/6480829017/job/17597132320?pr=430

See logs attached.

At first glance it seems related to watchers so first thing to pop in mind could be a missing mutex on cache access, related to this pull-request: https://github.com/netobserv/network-observability-operator/pull/449