[LIVY-697] Rsc client cannot resolve the hostname of driver in yarn-cluster mode

[runzhiwang]

What changes were proposed in this pull request?

[LIVY-697] Rsc client cannot resolve the hostname of driver in yarn-cluster mode

1. The content of Driver in /etc/hosts are as follows:
   127.0.0.1 localhost
   10.10.10.10 test_hostname

2. The content of Driver in /etc/hostname are as follows:
   test_hostname

3. The findLocalAddress method in livy cannot return 10.10.10.10, but return test_hostname.
   Because the test_hostname point to 10.10.10.10, which doesn't pass the check
   address.isLoopbackAddress(), so findLocalAddress return test_hostname .

4. The rsc client cannot resolve the test_hostname, which cause rsc client cannot connect to
   driver.

5. The findLocalAddress method in livy can return 10.10.10.10 as expected if the content
   of Driver in /etc/hosts are as follows, which is not correct in our environment.
   127.0.0.1 localhost
   127.0.0.1 test_hostname

6. Though I can modify the findLocalAddress method to return 10.10.10.10, but it maybe cause
   error if the machine has multiple network cards. So, rsc client gets the driver ip from the
   connection.

How was this patch tested?

1. The content of Driver in /etc/hosts are as follows:
   127.0.0.1 localhost
   127.0.0.1 test_hostname

2. The content of Driver in /etc/hostname are as follows:
   test_hostname

3. rsc client can get the driver ip in connection, and connect to driver successfully.

[codecov-io]

Codecov Report

Merging #246 into master will increase coverage by 0.04%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #246      +/-   ##
============================================
+ Coverage     68.08%   68.12%   +0.04%     
  Complexity      939      939              
============================================
  Files           101      101              
  Lines          5853     5855       +2     
  Branches        886      886              
============================================
+ Hits           3985     3989       +4     
+ Misses         1296     1295       -1     
+ Partials        572      571       -1

Impacted Files	Coverage Δ	Complexity Δ
...main/java/org/apache/livy/rsc/ContextLauncher.java	66.34% <100%> (+0.32%)	13 <0> (ø)	⬇️
...ain/java/org/apache/livy/rsc/driver/RSCDriver.java	80.75% <0%> (ø)	45% <0%> (ø)	⬇️
...c/main/scala/org/apache/livy/repl/ReplDriver.scala	33.33% <0%> (+2.56%)	7% <0%> (ø)	⬇️
...cala/org/apache/livy/scalaapi/ScalaJobHandle.scala	55.88% <0%> (+2.94%)	7% <0%> (ø)	⬇️

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[jerryshao]

LGTM.