SPARK-2481: The environment variables SPARK_HISTORY_OPTS is covered in spark-env.sh

Author: witgo <witgo@qq.com>
Author: GuoQiang Li <witgo@qq.com>

Closes #1341 from witgo/history_env and squashes the following commits:

b4fd9f8 [GuoQiang Li] review commit
0ebe401 [witgo] *-history-server.sh load spark-config.sh

(cherry picked from commit 9f04db17e50568d5580091add9100693177d7c4f)
Signed-off-by: Andrew Or <andrewor14@gmail.com>