[SPARK-10918] [CORE] Prevent task failed for executor kill by driver

[shenh062326]

When dynamicAllocation is enabled, when a executor was idle timeout, it will be kill by driver, if a task offer to the executor at the same time, the task will failed due to executor lost.

1. Before scheduler a task to a executor, check if it has been killed.
2. Call executorManager.onExecutorBusy before scheduler task.

[SparkQA]

Test build #43230 has finished for PR 8975 at commit 88c9c3e.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds the following public classes (experimental):
  • case class LogicalRelation(

[SparkQA]

Test build #43235 has finished for PR 8975 at commit 18cbf73.

• This patch fails MiMa tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #43915 has finished for PR 8975 at commit 6215f52.

• This patch fails Scala style tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #43916 has finished for PR 8975 at commit de47fb6.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[andrewor14]

@shenh062326 I've closed the issue because it duplicates SPARK-9552. Let's also close this PR because I believe #7888 is a better approach.

[vanzin]

@shenh062326 could you close this PR?