[SPARK-15300] Fix writer lock conflict when remove a block

## What changes were proposed in this pull request?

A writer lock could be acquired when 1) create a new block 2) remove a block 3) evict a block to disk. 1) and 3) could happen in the same time within the same task, all of them could happen in the same time outside a task. It's OK that when someone try to grab the write block for a block, but the block is acquired by another one that has the same task attempt id.

This PR remove the check.

## How was this patch tested?

Updated existing tests.

Author: Davies Liu <davies@databricks.com>

Closes #13082 from davies/write_lock_conflict.

core/src/main/scala/org/apache/spark/storage/BlockInfoManager.scala

@@ -228,10 +228,7 @@ private[storage] class BlockInfoManager extends Logging {
       infos.get(blockId) match {
         case None => return None
         case Some(info) =>
-          if (info.writerTask == currentTaskAttemptId) {
-            throw new IllegalStateException(
-              s"Task $currentTaskAttemptId has already locked $blockId for writing")
-          } else if (info.writerTask == BlockInfo.NO_WRITER && info.readerCount == 0) {
+          if (info.writerTask == BlockInfo.NO_WRITER && info.readerCount == 0) {
             info.writerTask = currentTaskAttemptId
             writeLocksByTask.addBinding(currentTaskAttemptId, blockId)
             logTrace(s"Task $currentTaskAttemptId acquired write lock for $blockId")

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

@@ -208,16 +208,14 @@ class BlockInfoManagerSuite extends SparkFunSuite with BeforeAndAfterEach {
     }
   }
 
-  test("cannot call lockForWriting while already holding a write lock") {
+  test("cannot grab a writer lock while already holding a write lock") {
     withTaskId(0) {
       assert(blockInfoManager.lockNewBlockForWriting("block", newBlockInfo()))
       blockInfoManager.unlock("block")
     }
     withTaskId(1) {
       assert(blockInfoManager.lockForWriting("block").isDefined)
-      intercept[IllegalStateException] {
-        blockInfoManager.lockForWriting("block")
-      }
+      assert(blockInfoManager.lockForWriting("block", false).isEmpty)
       blockInfoManager.assertBlockIsLockedForWriting("block")
     }
   }