Fix incorrect state when hostname resolution fails (#96)

This PR is much less ambitious than #94. In this case, we just fix the
issue when the process is already started, but an error in the
resolution of the hostname leads to an incorrect internal state.

Without this patch, the `new_state` will be `:ok`, as that is the return
from the logger function.
Afterwards, when going to the `terminate` callback, then we try to call
`EventHandler.detach(state.handler_ids)`, which translates to
`EventHandler.detach(:ok.handler_ids)` and fails

lib/telemetry_metrics_statsd.ex

@@ -511,6 +511,8 @@ defmodule TelemetryMetricsStatsd do
             "Failed to resolve the hostname #{host}: #{inspect(reason)}. " <>
               "Using the previously resolved address of #{:inet.ntoa(current_address)}."
           )
+
+          state
       end
 
     Process.send_after(self(), :resolve_host, interval)