ZEPPELIN-3296. Reorg livy integration test to minimize livy session

### What is this PR for?
Just refactor livy integration test to minuze livy session so that we can reduce the livy build time.

### What type of PR is it?
[Refactoring]

### Todos
* [ ] - Task

### What is the Jira issue?
* https://issues.apache.org/jira/browse/ZEPPELIN-3296

### How should this be tested?
* Travis CI pass

### Screenshots (if appropriate)

### Questions:
* Does the licenses files need update? No
* Is there breaking changes for older versions? No
* Does this needs documentation? No

Author: Jeff Zhang <zjffdu@apache.org>

Closes apache#2844 from zjffdu/ZEPPELIN-3296 and squashes the following commits:

206ea3e [Jeff Zhang] ZEPPELIN-3296. Reorg livy integration test to minimize livy session

.travis.yml

@@ -114,17 +114,16 @@ matrix:
       dist: trusty
       env: PYTHON="3" SCALA_VER="2.10" SPARK_VER="1.6.3" HADOOP_VER="2.6" PROFILE="-Pspark-1.6 -Phadoop2 -Phadoop-2.6 -Pscala-2.10" SPARKR="true" BUILD_FLAG="package -DskipTests -DskipRat -am" TEST_FLAG="test -DskipRat -am" MODULES="-pl spark/interpreter,spark/spark-dependencies" TEST_PROJECTS="-Dtest=org.apache.zeppelin.spark.* -DfailIfNoTests=false"
 
-    # Test python/pyspark with python 2, livy 0.5
     - sudo: required
       dist: trusty
       jdk: "openjdk7"
-      env: PYTHON="2" SCALA_VER="2.10" SPARK_VER="1.6.3" HADOOP_VER="2.6" LIVY_VER="0.5.0-incubating" PROFILE="-Pspark-1.6 -Phadoop2 -Phadoop-2.6 -Pscala-2.10" BUILD_FLAG="install -am -DskipTests -DskipRat" TEST_FLAG="verify -DskipRat" MODULES="-pl livy" TEST_PROJECTS="-Dpyspark.test.exclude='' -DfailIfNoTests=false"
+      env: PYTHON="2" SPARK_VER="1.6.3" HADOOP_VER="2.6" LIVY_VER="0.5.0-incubating" PROFILE="" BUILD_FLAG="install -am -DskipTests -DskipRat" TEST_FLAG="verify -DskipRat" MODULES="-pl livy" TEST_PROJECTS=""
 
-    # Test python/pyspark with python 3, livy 0.5
+    # Test livy 0.5 with spark 2.2.0 under python3
     - sudo: required
       dist: trusty
-      jdk: "openjdk7"
-      env: PYTHON="3" SCALA_VER="2.11" SPARK_VER="2.0.0" HADOOP_VER="2.6" LIVY_VER="0.5.0-incubating" PROFILE="-Pspark-2.0 -Phadoop3 -Phadoop-2.6 -Pscala-2.11" BUILD_FLAG="install -am -DskipTests -DskipRat" TEST_FLAG="verify -DskipRat" MODULES="-pl livy" TEST_PROJECTS="-Dpyspark.test.exclude='' -DfailIfNoTests=false"
+      jdk: "openjdk8"
+      env: PYTHON="3" SPARK_VER="2.2.0" HADOOP_VER="2.6" LIVY_VER="0.5.0-incubating" PROFILE="" BUILD_FLAG="install -am -DskipTests -DskipRat" TEST_FLAG="verify -DskipRat" MODULES="-pl livy" TEST_PROJECTS=""
 
 before_install:
   # check files included in commit range, clear bower_components if a bower.json file has changed.