Review Request 46133: Simplify `Credentials`; kill `ZooKeeperClient` dep.

[John Sirois]

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This is an automatically generated e-mail. To reply, visit:
https://reviews.apache.org/r/46133/
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Review request for Aurora, Bill Farner and Zameer Manji.


Bugs: AURORA-1468
    https://issues.apache.org/jira/browse/AURORA-1468


Repository: aurora


Description
-------

The Curator discovery code will need to be configured from the same
command line flags and code as the commons discovery code.  This
simplifies Credentials to be a simple struct and adapts from the
`Credentials.NONE` null-object to use of `Optional` in consumers.

 commons/src/main/java/org/apache/aurora/common/zookeeper/Credentials.java      
                   |  90 +++++++++++++++++++++++++++++++
 commons/src/main/java/org/apache/aurora/common/zookeeper/ZooKeeperClient.java  
                   | 147 ++++++--------------------------------------------
 
commons/src/main/java/org/apache/aurora/common/zookeeper/testing/BaseZooKeeperClientTest.java
     |  15 +++---
 commons/src/test/java/org/apache/aurora/common/zookeeper/GroupTest.java        
                   |   3 +-
 
commons/src/test/java/org/apache/aurora/common/zookeeper/ZooKeeperClientTest.java
                 |  37 +------------
 
src/main/java/org/apache/aurora/scheduler/discovery/ServiceDiscoveryModule.java 
                  |  13 ++---
 src/main/java/org/apache/aurora/scheduler/log/mesos/MesosLogStreamModule.java  
                   |  30 +++++++----
 
src/main/java/org/apache/aurora/scheduler/zookeeper/guice/client/ZooKeeperClientModule.java
       |  21 +++++---
 
src/main/java/org/apache/aurora/scheduler/zookeeper/guice/client/flagged/FlaggedClientConfig.java
 |  20 +++----
 src/test/java/org/apache/aurora/scheduler/app/SchedulerIT.java                 
                   |   6 +--
 10 files changed, 172 insertions(+), 210 deletions(-)


Diffs
-----

  commons/src/main/java/org/apache/aurora/common/zookeeper/Credentials.java 
PRE-CREATION 
  commons/src/main/java/org/apache/aurora/common/zookeeper/ZooKeeperClient.java 
41ae035bdd780027f459ec42c39fb6190a963182 
  
commons/src/main/java/org/apache/aurora/common/zookeeper/testing/BaseZooKeeperClientTest.java
 b9eaedb1f6740fdaf65bd0fa2613d4dd914536f7 
  commons/src/test/java/org/apache/aurora/common/zookeeper/GroupTest.java 
9127b6e569618f30b74bae2fc7665a92bc30d735 
  
commons/src/test/java/org/apache/aurora/common/zookeeper/ZooKeeperClientTest.java
 537d41e2f6a2d56318e50219c8d848a0e253ecd5 
  
src/main/java/org/apache/aurora/scheduler/discovery/ServiceDiscoveryModule.java 
c14162fa59bec41e00d8604e7659ca3b925f7a23 
  src/main/java/org/apache/aurora/scheduler/log/mesos/MesosLogStreamModule.java 
5daafa9234d20dfcfd9a6cc81508836efe39f1f0 
  
src/main/java/org/apache/aurora/scheduler/zookeeper/guice/client/ZooKeeperClientModule.java
 4239a867119699267ff8e663a2827feb751fbb79 
  
src/main/java/org/apache/aurora/scheduler/zookeeper/guice/client/flagged/FlaggedClientConfig.java
 5b59d55b8e58d0231a18da9813045a9d1dd70be3 
  src/test/java/org/apache/aurora/scheduler/app/SchedulerIT.java 
89b2813773c2c4bf211883e9d67592b37852776c 

Diff: https://reviews.apache.org/r/46133/diff/


Testing
-------

Locally green:
```
./gradlew -Pq build
./src/test/sh/org/apache/aurora/e2e/test_end_to_end.sh
```


Thanks,

John Sirois