Report features to master before reporting errors

As soon as we report an error to the master, it kills our process.
This in turn prevents us from reporting the features loaded before
the error and getting restarted when those change.
https://github.com/burke/zeus/blob/0cd1c4fad7c214a4a842665922803b7e2bac3347/go/processtree/slavenode.go#L223-L226

Instead, we want to report features before reporting the error but ensure
that we eventually report the error even if feature reporting fails.

rubygem/lib/zeus.rb

@@ -189,23 +189,25 @@ def report_error_to_master(local, error)
 
     def run_action(socket, identifier, feature_pipe_w)
       # Now we run the action and report its success/fail status to the master.
-      loaded = false
       features, err = Zeus::LoadTracking.features_loaded_by do
         plan.after_fork unless identifier == :boot
         plan.send(identifier)
-        loaded = true
-        socket.write "R:OK\0"
       end
 
-      # the master wants to know about the files that running the
-      # action caused us to load. If we received an error, report them
-      # syncronously and along with the error. Otherwise, report them
-      # in a new thread and start listening for commands.
       if err
-        report_error_to_master(socket, err)
-        notify_features(feature_pipe_w, features) unless loaded
-        feature_pipe_w.close
+        # If we received an error, report features to the master syncronously.
+        # We need to do this before reporting the error to the master
+        # otherwise it will kill us before we can report features.
+        begin
+          notify_features(feature_pipe_w, features)
+          feature_pipe_w.close
+        ensure
+          report_error_to_master(socket, err)
+        end
       else
+        # If we booted successfully, report features in a new thread
+        # so we can immediately begin listening for commands.
+        socket.write "R:OK\0"
         Thread.new { notify_features(feature_pipe_w, features) }
       end
     end