fix: do not use wrong hostname provided by getent

When we run getent hosts <ip> inside the amqp-statefulset, this command will sometimes return hostnames in the format of <pod-IPv4-address>.<namespace>.pod.<cluster-domain> but we need the format <pod-hostname>.<namespace>.pod.<cluster-domain>.

For now, we use a workaround where we wait until the getent hosts returns an address with the desired format since this problem often causes our integration tests to fail.

Issue: #662