daemon: don't hold endpoint BuildMutex while deleting
daemon: don't hold endpoint BuildMutex while deleting

Stopping the endpoint's EventQueue is sufficient, as when we stop the queue and wait for
in-flight regenerations to complete before proceeding further and cleaning up various state
relevant to the endpoint. Stopping the endpoint's EventQueue means that no events which are
enqueued after stopping (e.g., regenerations) are processed, and as such they are no-ops.

Signed-off by: Ian Vernon <ian@cilium.io>

tklauser/cilium,cilium/cilium,tgraf/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,cilium-team/cilium,tgraf/cilium,tgraf/cilium,cilium-team/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium