Branch 2.7 cherry picked commits (#2396)

* [AMBARI-24653] YARN Timeline server v2 related system tests fail. (#2367)

* [AMBARI-24653] YARN Timeline server v2 related system tests fail.

* [AMBARI-24653] YARN Timeline server v2 related system tests fail.

* AMBARI-24661. While registering agent can miss updates from server (aonishuk)

* [AMBARI-24679] Fix race condition in agent during registration and topology updates. (#2368)
3 files changed