[SPARK-5771] Number of Cores in Completed Applications of Standalone Master...

[SPARK-5771] Number of Cores in Completed Applications of Standalone Master Web Page always be 0 if sc.stop() is called

In Standalone mode, the number of cores in Completed Applications of the Master Web Page will always be zero, if sc.stop() is called.
But the number will always be right, if sc.stop() is not called.
The reason maybe:
after sc.stop() is called, the function removeExecutor of class ApplicationInfo will be called, thus reduce the variable coresGranted to zero. The variable coresGranted is used to display the number of Cores on the Web Page.

Author: guliangliang <guliangliang@qiyi.com>

Closes #4567 from marsishandsome/Spark5771 and squashes the following commits:

694796e [guliangliang] remove duplicate code
a20e390 [guliangliang] change to Cores Using & Requested
0c19c95 [guliangliang] change Cores to Cores (max)
cfbd97d [guliangliang] [SPARK-5771] Number of Cores in Completed Applications of Standalone Master Web Page always be 0 if sc.stop() is called