[SPARK-19803][TEST] flaky BlockManagerReplicationSuite test failure

## What changes were proposed in this pull request?

200ms may be too short. Give more time for replication to happen and new block be reported to master

## How was this patch tested?

test manully

Author: uncleGen <hustyugm@gmail.com>
Author: dylon <hustyugm@gmail.com>

Closes #17144 from uncleGen/SPARK-19803.

core/src/test/scala/org/apache/spark/storage/BlockManagerReplicationSuite.scala

@@ -489,12 +489,12 @@ class BlockManagerProactiveReplicationSuite extends BlockManagerReplicationBehav
       Thread.sleep(200)
     }
 
-    // giving enough time for replication complete and locks released
-    Thread.sleep(500)
-
-    val newLocations = master.getLocations(blockId).toSet
+    val newLocations = eventually(timeout(5 seconds), interval(10 millis)) {
+      val _newLocations = master.getLocations(blockId).toSet
+      assert(_newLocations.size === replicationFactor)
+      _newLocations
+    }
     logInfo(s"New locations : $newLocations")
-    assert(newLocations.size === replicationFactor)
     // there should only be one common block manager between initial and new locations
     assert(newLocations.intersect(blockLocations.toSet).size === 1)