Fix memory leak when performing healthcheck on backends.
Fix memory leak when performing healthcheck on backends.

- Replace time.Tick one-time usage with time.After to avoid leaving a
channel open.

[#88198872]

cloudfoundry-incubator/switchboard,cloudfoundry-incubator/switchboard,cloudfoundry-incubator/switchboard,cloudfoundry-incubator/switchboard