Fix flakiness of migrate test

This test became flaky when the default write type became async-through.
This is because when the migrate is configured to delete the source,
sometimes, that inode is NOT persisted, so it is not removed from the
UFS. Then, on the `exists` call, it will loadMetadata from UFS, and it
will load the file from UFS and the deleted file will "return".

pr-link: #9884
change-id: cid-d9c66bd59b9e4180756dc13a8ac243f6951aafbe

tests/src/test/java/alluxio/job/migrate/MigrateIntegrationTest.java

@@ -15,6 +15,8 @@
 import alluxio.client.WriteType;
 import alluxio.client.file.FileInStream;
 import alluxio.client.file.FileOutStream;
+import alluxio.grpc.CreateFilePOptions;
+import alluxio.grpc.WritePType;
 import alluxio.job.JobIntegrationTest;
 import alluxio.job.wire.JobInfo;
 
@@ -103,7 +105,8 @@ public void migrateDirectory() throws Exception {
    * Creates a file with the given name containing TEST_BYTES.
    */
   private void createFileWithTestBytes(String filename) throws Exception {
-    try (FileOutStream out = mFileSystem.createFile(new AlluxioURI(filename))) {
+    try (FileOutStream out = mFileSystem.createFile(new AlluxioURI(filename),
+        CreateFilePOptions.newBuilder().setWriteType(WritePType.CACHE_THROUGH).build())) {
       out.write(TEST_BYTES);
     }
     Assert.assertTrue(mFileSystem.exists(new AlluxioURI(filename)));