test/runtime: fix flake on non-ready endpoints
test/runtime: fix flake on non-ready endpoints

Ensure that all endpoints exist and are ready before attempting to
extract a specific endpoint from GetAllEndpointsIds results.

Follows commit 3738680a91eb ("test/runtime: Fix flake on reserved:init
endpoints") which introduced a similar check before calls to
GetEndpointIds.

Signed-off-by: Tobias Klauser <059b8b880f8441509ec8a65b50b4c6ae74ebea76@cilium.io>

michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,cilium/cilium,cilium/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium/cilium,michi-covalent/cilium,cilium/cilium