[SPARK-3606] [yarn] Correctly configure AmIpFilter for Yarn HA (1.1 vers...

...ion).

This is a backport of SPARK-3606 to branch-1.1. Some of the code had to be
duplicated since branch-1.1 doesn't have the cleanup work that was done to
the Yarn codebase.

I don't know whether the version issue in yarn/alpha/pom.xml was intentional,
but I couldn't compile the code without fixing it.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #2497 from vanzin/SPARK-3606-1.1 and squashes the following commits:

4fd3c27 [Marcelo Vanzin] Remove unused imports.
75cde8c [Marcelo Vanzin] Scala is weird.
b27ebda [Marcelo Vanzin] Review feedback.
72ceafb [Marcelo Vanzin] Undelete needed import.
61162a6 [Marcelo Vanzin] Use separate config for each param instead of json.
3b7205f [Marcelo Vanzin] Review feedback.
b3b3e50 [Marcelo Vanzin] [SPARK-3606] [yarn] Correctly configure AmIpFilter for Yarn HA (1.1 version).