Final iteration, fixing a couple mistakes for query exceptions

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/Query.cs

@@ -177,12 +177,10 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
             {
                 HasError = true;
                 UnwrapDbException(dbe);
-                conn?.Dispose();
             }
             catch (Exception)
             {
                 HasError = true;
-                conn?.Dispose();
                 throw;
             }
             finally

src/Microsoft.SqlTools.ServiceLayer/QueryExecution/QueryExecutionService.cs

@@ -213,6 +213,7 @@ namespace Microsoft.SqlTools.ServiceLayer.QueryExecution
             }
             catch (InvalidOperationException e)
             {
+                // If this exception occurred, we most likely were trying to cancel a completed query
                 await requestContext.SendResult(new QueryCancelResult
                 {
                     Messages = e.Message