EtcdHealthIndicator should not poll etcd if spring.cloud.etcd.enabled=false

[otrosien]

at the moment actuator health hangs for quite some time waiting for an etcd reply on localhost:4001, which should not be even contacted if the configuration disabled spring.cloud.etcd IMO.

[otrosien]

alternatively, exclude etcdHealthIndicator completely if etcd is disabled..?
the more I think about it, the more it actually makes sense to just exlude it. Application health status should be UP in the end, if admin decides to not use etcd. @spencergibb wdyt?

[otrosien]

closing PR#22 - so the solution should probably look like this:

• Do not add etcd health checks if spring.cloud.etcd.enabled=false or spring.cloud.etcd.healthcheck.enabled=false (new config property)