[SPARK-4626] Kill a task only if the executorId is (still) registered with the scheduler

Author: roxchkplusony <roxchkplusony@gmail.com>

Closes #3483 from roxchkplusony/bugfix/4626 and squashes the following commits:

aba9184 [roxchkplusony] replace warning message per review
5e7fdea [roxchkplusony] [SPARK-4626] Kill a task only if the executorId is (still) registered with the scheduler

(cherry picked from commit 84376d31392858f7df215ddb3f05419181152e68)
Signed-off-by: Reynold Xin <rxin@databricks.com>
[SPARK-4613][Core] Java API for JdbcRDD

This PR introduces a set of Java APIs for using `JdbcRDD`:

1. Trait (interface) `JdbcRDD.ConnectionFactory`: equivalent to the `getConnection: () => Connection` parameter in `JdbcRDD` constructor.
2. Two overloaded versions of `Jdbc.create`: used to create `JavaRDD` that wraps a `JdbcRDD`.

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Author: Cheng Lian <lian@databricks.com>

Closes #3478 from liancheng/japi-jdbc-rdd and squashes the following commits:

9a54625 [Cheng Lian] Only shutdowns a single DB rather than the whole Derby driver
d4cedc5 [Cheng Lian] Moves Java JdbcRDD test case to a separate test suite
ffcdf2e [Cheng Lian] Java API for JdbcRDD

(cherry picked from commit 120a350240f58196eafcb038ca3a353636d89239)
Signed-off-by: Matei Zaharia <matei@databricks.com>
[SPARK-4619][Storage]delete redundant time suffix

Time suffix exists in Utils.getUsedTimeMs(startTime), no need to append again, delete that

Author: maji2014 <maji3@asiainfo.com>

Closes #3475 from maji2014/SPARK-4619 and squashes the following commits:

df0da4e [maji2014] delete redundant time suffix

(cherry picked from commit ceb628197099e6c598cde1564ed9c1c3681ea955)
Signed-off-by: Reynold Xin <rxin@databricks.com>