Fix Reason NameError using constants included in MiqServer

Due to module inclusion spaghetti, it's easier and less confusing
to reference the Reason constants consistently in the MiqServer class,
which is the ultimate destination for all of these modules.

Fixes ManageIQ#13901 introduced in ManageIQ#13805

https://bugzilla.redhat.com/show_bug.cgi?id=1395736

app/models/miq_server/worker_management/monitor.rb

@@ -100,7 +100,7 @@ def check_not_responding(class_name = nil)
   end
 
   def monitor_reason_not_responding?(w)
-    [Reason::NOT_RESPONDING, Reason::MEMORY_EXCEEDED].include?(worker_get_monitor_reason(w.pid)) || w.stopping_for_too_long?
+    [MiqServer::NOT_RESPONDING, MiqServer::MEMORY_EXCEEDED].include?(worker_get_monitor_reason(w.pid)) || w.stopping_for_too_long?
   end
 
   def do_system_limit_exceeded
@@ -113,7 +113,7 @@ def do_system_limit_exceeded
       msg = "#{w.format_full_log_msg} is being stopped because system resources exceeded threshold, it will be restarted once memory has freed up"
       _log.warn(msg)
       MiqEvent.raise_evm_event_queue_in_region(w.miq_server, "evm_server_memory_exceeded", :event_details => msg, :type => w.class.name)
-      restart_worker(w, Reason::MEMORY_EXCEEDED)
+      restart_worker(w, MiqServer::MEMORY_EXCEEDED)
       break
     end
   end

app/models/miq_server/worker_management/monitor/validation.rb

@@ -14,7 +14,7 @@ def validate_worker(w)
       msg = "#{w.format_full_log_msg} has not responded in #{Time.now.utc - w.last_heartbeat} seconds, restarting worker"
       _log.error(msg)
       MiqEvent.raise_evm_event_queue(w.miq_server, "evm_worker_not_responding", :event_details => msg, :type => w.class.name)
-      restart_worker(w, Reason::NOT_RESPONDING)
+      restart_worker(w, MiqServer::NOT_RESPONDING)
       return false
     end
 

spec/models/miq_server/worker_monitor_spec.rb

@@ -362,6 +362,12 @@
           server.setup_drb_variables
         end
 
+        it "should mark not responding if not recently heartbeated" do
+          worker.update(:last_heartbeat => 20.minutes.ago)
+          expect(server.validate_worker(worker)).to be_falsey
+          expect(worker.reload.status).to eq(MiqWorker::STATUS_STOPPING)
+        end
+
         context "for excessive memory" do
           before { worker.memory_usage = 2.gigabytes }