Fix the rest of the completion tests with the new analysis driver.

pkg/analysis_server/lib/src/domain_completion.dart

Index: pkg/analysis_server/lib/src/domain_completion.dart
diff --git a/pkg/analysis_server/lib/src/domain_completion.dart b/pkg/analysis_server/lib/src/domain_completion.dart
index 6bad4431a2ab122d8773b9cdd4259df474e243cb..436254e5a833179dd48a1e211949607c8f8af250 100644
--- a/pkg/analysis_server/lib/src/domain_completion.dart
+++ b/pkg/analysis_server/lib/src/domain_completion.dart
@@ -138,7 +138,7 @@ class CompletionDomainHandler implements RequestHandler {
     if (server.options.enableNewAnalysisDriver) {
       result = await server.getAnalysisResult(params.file);
 
-      if (result == null) {
+      if (result == null || !result.exists) {
         server.sendResponse(new Response.unknownSource(request));
         return;
       }