agents: remove ASSERT that can be ignored

Instead of updating the ASSERT with additional error info, remove them
since there's nothing to do in case there's an error.

agents/otlp/src/otlp_agent.cc

@@ -403,12 +403,9 @@ void OTLPAgent::span_msg_cb_(nsuv::ns_async*, OTLPAgent* agent) {
 
   agent->got_proc_metrics();
   for (auto& item : agent->env_metrics_map_) {
-    int r = item.second.metrics_.Update(thr_metrics_cb_, agent);
-    // The UV_ESRCH and UV_EBADF errors can happen during the env shutdown
-    // process. Leaving this assertion for the moment in case another error is
-    // returned at some point.
-    // TODO(santi): Remove the assertion
-    ASSERT(r == 0 || r == UV_ESRCH || r == UV_EBADF);
+    // Retrieve metrics from the Metrics API. Ignore any return error since
+    // there's nothing to be done.
+    item.second.metrics_.Update(thr_metrics_cb_, agent);
   }
 }
 

agents/statsd/src/statsd_agent.cc

@@ -731,14 +731,9 @@ void StatsDAgent::metrics_timer_cb_(nsuv::ns_timer*, StatsDAgent* agent) {
        it != agent->env_metrics_map_.end();
        ++it) {
     ThreadMetrics& e_metrics = std::get<1>(*it);
-    // Retrieve metrics from the Metrics API.
-    int r = e_metrics.Update(env_metrics_cb_, agent);
-    // The UV_ESRCH and UV_EBADF errors can happen during the env shutdown
-    // process.
-    // Leaving this assertion for the moment in case another error is returned
-    // at some point.
-    // TODO(santi): Remove the assertion.
-    ASSERT(r == 0 || r == UV_ESRCH || r == UV_EBADF);
+    // Retrieve metrics from the Metrics API. Ignore any return error since
+    // there's nothing to be done.
+    e_metrics.Update(env_metrics_cb_, agent);
   }
 
   // Get and send proc metrics

agents/zmq/src/zmq_agent.cc

@@ -1638,14 +1638,9 @@ void ZmqAgent::metrics_timer_cb(nsuv::ns_timer*, ZmqAgent* agent) {
     EnvMetricsStor& stor = std::get<1>(*it);
     // Reset fetching flag.
     stor.fetching = false;
-    // Retrieve metrics from the Metrics API.
+    // Retrieve metrics from the Metrics API. Ignore any return error since
+    // there's nothing to be done.
     int r = stor.t_metrics.Update(env_metrics_cb, agent);
-    // The UV_ESRCH and UV_EBADF errors can happen during the env shutdown
-    // process.
-    // Leaving this assertion for the moment in case another error is returned
-    // at some point.
-    // TODO(santi): Remove the assertion.
-    ASSERT(r == 0 || r == UV_ESRCH || r == UV_EBADF);
     if (r == 0)
       stor.fetching = true;
   }