[FLINK-10799][yarn] YARN mode JobManager JVM memory args add -XmsXXXm

[xinchun-wang]

What is the purpose of the change

When start JobManager on Yarn mode, only set -Xmx parameter , add -Xms also to avoid high frequency full gc at start up phase.

Brief change log

• add -Xms when start up JobManager, the value equals -Xmx

Verifying this change

This change added tests and can be verified as follows:
Change unit test method testSetupApplicationMasterContainer in YarnClusterDescriptorTest

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): no
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[tillrohrmann]

Thanks for your contribution @xinchun-wang. LGTM. Merging.