ZOOKEEPER: zk: not authenticated

Hi,
I am trying to configure Burrow with Zookeeper server started with jaas.conf file. Recently I have solved the problems with KAFKA SSL/SASL (https://github.com/linkedin/Burrow/issues/333), but now I have a problem with this configuration. Zookeeper is started with DigestLoginModule.

jaas.conf:

```
Server {
org.apache.zookeeper.server.auth.DigestLoginModule required
admin="admin_pw";
};
```

zookeeper env:
`
SERVER_JVMFLAGS="-Djava.security.auth.login.config=/opt/zookeeper-3.4.9/conf/jaas.conf"
`

And Burrow with the following configuration:

```
[general]
access-control-allow-origin="*"

[logging]
level="debug"

[zookeeper]
servers=["183.155.2.197:2181"]

[client-profile.kafka-profile]
kafka-version="1.0.0"
client-id="burrow-client"
sasl="mysasl"
tls="mytls"

[sasl.mysasl]
username="admin"
password="admin-secret"
handshake-first=true

[tls.mytls]
noverify=true

[cluster.my_cluster]
class-name="kafka"
client-profile="kafka-profile"
servers=["183.155.2.197:9094"]
topic-refresh=120
offset-refresh=10

[consumer.consumer_kafka]
class-name="kafka"
cluster="my_cluster"
servers=["183.155.2.197:9094"]
client-profile="kafka-profile"
start-latest=false
offsets-topic="__consumer_offsets"
group-blacklist="^(console-consumer-|python-kafka-consumer-).*$"

[consumer.consumer_zk]
class-name="kafka_zk"
cluster="my_cluster"
servers=["183.155.2.197:2181"]
zookeeper-timeout=30
group-blacklist="^(console-consumer-|python-kafka-consumer-).*$"

[httpserver.default]
address=":8002"

```

After I have invoked this command on zookeeper:

`./zookeeper-security-migration.sh --zookeeper.acl secure --zookeeper.connect 183.155.2.197:2181`

i get the following error:

```
{"level":"info","ts":1517822857.9368994,"msg":"configuring","type":"coordinator","name":"zookeeper"}
{"level":"info","ts":1517822857.9369743,"msg":"configuring","type":"coordinator","name":"storage"}
{"level":"info","ts":1517822857.9370685,"msg":"configuring","type":"module","coordinator":"storage","class":"inmemory","name":"default"}
{"level":"info","ts":1517822857.937189,"msg":"configuring","type":"coordinator","name":"evaluator"}
{"level":"info","ts":1517822857.9372375,"msg":"configuring","type":"module","coordinator":"evaluator","class":"caching","name":"default"}
{"level":"info","ts":1517822857.9373174,"msg":"configuring","type":"coordinator","name":"httpserver"}
{"level":"info","ts":1517822857.9373896,"msg":"configuring","type":"coordinator","name":"notifier"}
{"level":"info","ts":1517822857.9374373,"msg":"configuring","type":"coordinator","name":"cluster"}
{"level":"info","ts":1517822857.937574,"msg":"configuring","type":"module","coordinator":"cluster","class":"kafka","name":"local_cluster"}
{"level":"info","ts":1517822857.937773,"msg":"configuring","type":"coordinator","name":"consumer"}
{"level":"info","ts":1517822857.937828,"msg":"configuring","type":"module","coordinator":"consumer","class":"kafka","name":"consumer_kafka"}
{"level":"info","ts":1517822857.9383683,"msg":"configuring","type":"module","coordinator":"consumer","class":"kafka_zk","name":"consumer_zk"}
{"level":"info","ts":1517822857.938516,"msg":"starting","type":"coordinator","name":"zookeeper"}
{"level":"info","ts":1517822857.9393747,"msg":"Connected to 183.155.2.197:2181","type":"coordinator","name":"zookeeper"}
{"level":"info","ts":1517822857.9441001,"msg":"Authenticated: id=171529193565388812, timeout=6000","type":"coordinator","name":"zookeeper"}
{"level":"info","ts":1517822857.944146,"msg":"Re-submitting `0` credentials after reconnect","type":"coordinator","name":"zookeeper"}
{"level":"error","ts":1517822857.9470801,"msg":"cannot create root path","type":"coordinator","name":"zookeeper","error":"zk: not authenticated"}
Burrow failed at February 5, 2018 at 9:27am (UTC)

```

Is it possible to pass user/password to zookeeper ?

Start by tracing Burrow's zookeeper coordinator authentication setup, using the supplied JAAS and Zookeeper configuration as the reproduction case. Done means Burrow can authenticate to Zookeeper and create its root path without the "zk: not authenticated" error.

Written by the indexing model from the issue text.