UPdates to test suite
[SPARK-3154][STREAMING] Replace ConcurrentHashMap with mutable.HashMap and remove @volatile from 'stopped'

Since `sequenceNumberToProcessor` and `stopped` are both protected by the lock `sequenceNumberToProcessor`, `ConcurrentHashMap` and `volatile` is unnecessary. So this PR updated them accordingly.

Author: zsxwing <zsxwing@gmail.com>

Closes #3634 from zsxwing/SPARK-3154 and squashes the following commits:

0d087ac [zsxwing] Replace ConcurrentHashMap with mutable.HashMap and remove @volatile from 'stopped'
[SPARK-4785][SQL] Initilize Hive UDFs on the driver and serialize them with a wrapper

Different from Hive 0.12.0, in Hive 0.13.1 UDF/UDAF/UDTF (aka Hive function) objects should only be initialized once on the driver side and then serialized to executors. However, not all function objects are serializable (e.g. GenericUDF doesn't implement Serializable). Hive 0.13.1 solves this issue with Kryo or XML serializer. Several utility ser/de methods are provided in class o.a.h.h.q.e.Utilities for this purpose. In this PR we chose Kryo for efficiency. The Kryo serializer used here is created in Hive. Spark Kryo serializer wasn't used because there's no available SparkConf instance.

Author: Cheng Hao <hao.cheng@intel.com>
Author: Cheng Lian <lian@databricks.com>

Closes #3640 from chenghao-intel/udf_serde and squashes the following commits:

8e13756 [Cheng Hao] Update the comment
74466a3 [Cheng Hao] refactor as feedbacks
396c0e1 [Cheng Hao] avoid Simple UDF to be serialized
e9c3212 [Cheng Hao] update the comment
19cbd46 [Cheng Hao] support udf instance ser/de after initialization
SPARK-4338. [YARN] Ditch yarn-alpha.

Sorry if this is a little premature with 1.2 still not out the door, but it will make other work like SPARK-4136 and SPARK-2089 a lot easier.

Author: Sandy Ryza <sandy@cloudera.com>

Closes #3215 from sryza/sandy-spark-4338 and squashes the following commits:

1c5ac08 [Sandy Ryza] Update building Spark docs and remove unnecessary newline
9c1421c [Sandy Ryza] SPARK-4338. Ditch yarn-alpha.
Merge remote-tracking branch 'upstream/master' into SPARK-4417