[HOTFIX] Fix compilation error for Yarn 2.0.*-alpha

This was reported in https://issues.apache.org/jira/browse/SPARK-3445. There are API differences between the 0.23.* and the 2.0.*-alpha branches that are not accounted for when this code was introduced.

Author: Andrew Or <andrewor14@gmail.com>

Closes #2776 from andrewor14/fix-yarn-alpha and squashes the following commits:

ec94752 [Andrew Or] Fix compilation error for 2.0.*-alpha