Fix hang when debug adapter finishes executing

This change fixes a hang that was caused by the recent refactoring of host
process server implementations.  In the debug adapter implementation, the
PowerShellContext was not being disposed at shutdown which was causing the
process to stay open because the associated threads were still alive.
This change adds the necessary ProtocolServer.Shutdown implementation.

Author: daviwil

src/PowerShellEditorServices.Protocol/Server/DebugAdapter.cs

@@ -56,6 +56,17 @@ protected override void Initialize()
             this.SetRequestHandler(EvaluateRequest.Type, this.HandleEvaluateRequest);
         }
 
+        protected override void Shutdown()
+        {
+            Logger.Write(LogLevel.Normal, "Debug adapter is shutting down...");
+
+            if (this.editorSession != null)
+            {
+                this.editorSession.Dispose();
+                this.editorSession = null;
+            }
+        }
+
         #region Built-in Message Handlers
 
         protected async Task HandleLaunchRequest(

src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs

@@ -70,7 +70,11 @@ protected override void Shutdown()
         {
             Logger.Write(LogLevel.Normal, "Language service is shutting down...");
 
-            this.editorSession.Dispose();
+            if (this.editorSession != null)
+            {
+                this.editorSession.Dispose();
+                this.editorSession = null;
+            }
         }
 
         #region Built-in Message Handlers

test/PowerShellEditorServices.Test/Debugging/DebugServiceTests.cs

@@ -61,11 +61,7 @@ void debugService_BreakpointUpdated(object sender, BreakpointUpdatedEventArgs e)
 
         void debugService_DebuggerStopped(object sender, DebuggerStopEventArgs e)
         {
-            this.runnerContext.Post(
-                (o) =>
-                {
-                    this.debuggerStoppedQueue.Enqueue(e);
-                }, null);
+            this.debuggerStoppedQueue.Enqueue(e);
         }
 
         public void Dispose()
@@ -119,7 +115,6 @@ await this.debugService.SetBreakpoints(
             this.debugService.Continue();
 
             await this.AssertDebuggerStopped(this.debugScriptFile.FilePath, 9);
-            this.debugService.Continue();
 
             // Abort script execution early and wait for completion
             this.debugService.Abort();