[SPARK-19464][BUILD][HOTFIX] run-tests should use hadoop2.6

## What changes were proposed in this pull request?

After SPARK-19464, **SparkPullRequestBuilder** fails because it still tries to use hadoop2.3.

**BEFORE**
https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/72595/console
```
========================================================================
Building Spark
========================================================================
[error] Could not find hadoop2.3 in the list. Valid options  are ['hadoop2.6', 'hadoop2.7']
Attempting to post to Github...
 > Post successful.
```

**AFTER**
https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/72595/console
```
========================================================================
Building Spark
========================================================================
[info] Building Spark (w/Hive 1.2.1) using SBT with these arguments:  -Phadoop-2.6 -Pmesos -Pkinesis-asl -Pyarn -Phive-thriftserver -Phive test:package streaming-kafka-0-8-assembly/assembly streaming-flume-assembly/assembly streaming-kinesis-asl-assembly/assembly
Using /usr/java/jdk1.8.0_60 as default JAVA_HOME.
Note, this will be overridden by -java-home if it is set.
```

## How was this patch tested?

Pass the existing test.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #16858 from dongjoon-hyun/hotfix_run-tests.

R/pkg/inst/tests/testthat/test_utils.R

@@ -231,10 +231,7 @@ test_that("varargsToStrEnv", {
 test_that("basenameSansExtFromUrl", {
   x <- paste0("http://people.apache.org/~pwendell/spark-nightly/spark-branch-2.1-bin/spark-2.1.1-",
               "SNAPSHOT-2016_12_09_11_08-eb2d9bf-bin/spark-2.1.1-SNAPSHOT-bin-hadoop2.7.tgz")
-  y <- paste0("http://people.apache.org/~pwendell/spark-releases/spark-2.1.0-rc2-bin/spark-2.1.0-",
-              "bin-hadoop2.4-without-hive.tgz")
   expect_equal(basenameSansExtFromUrl(x), "spark-2.1.1-SNAPSHOT-bin-hadoop2.7")
-  expect_equal(basenameSansExtFromUrl(y), "spark-2.1.0-bin-hadoop2.4-without-hive")
   z <- "http://people.apache.org/~pwendell/spark-releases/spark-2.1.0--hive.tar.gz"
   expect_equal(basenameSansExtFromUrl(z), "spark-2.1.0--hive")
 })

dev/run-tests-jenkins.py

@@ -165,12 +165,6 @@ def main():
     if "test-maven" in ghprb_pull_title:
         os.environ["AMPLAB_JENKINS_BUILD_TOOL"] = "maven"
     # Switch the Hadoop profile based on the PR title:
-    if "test-hadoop2.2" in ghprb_pull_title:
-        os.environ["AMPLAB_JENKINS_BUILD_PROFILE"] = "hadoop2.2"
-    if "test-hadoop2.3" in ghprb_pull_title:
-        os.environ["AMPLAB_JENKINS_BUILD_PROFILE"] = "hadoop2.3"
-    if "test-hadoop2.4" in ghprb_pull_title:
-        os.environ["AMPLAB_JENKINS_BUILD_PROFILE"] = "hadoop2.4"
     if "test-hadoop2.6" in ghprb_pull_title:
         os.environ["AMPLAB_JENKINS_BUILD_PROFILE"] = "hadoop2.6"
     if "test-hadoop2.7" in ghprb_pull_title:

dev/run-tests.py

@@ -505,14 +505,14 @@ def main():
         # if we're on the Amplab Jenkins build servers setup variables
         # to reflect the environment settings
         build_tool = os.environ.get("AMPLAB_JENKINS_BUILD_TOOL", "sbt")
-        hadoop_version = os.environ.get("AMPLAB_JENKINS_BUILD_PROFILE", "hadoop2.3")
+        hadoop_version = os.environ.get("AMPLAB_JENKINS_BUILD_PROFILE", "hadoop2.6")
         test_env = "amplab_jenkins"
         # add path for Python3 in Jenkins if we're calling from a Jenkins machine
         os.environ["PATH"] = "/home/anaconda/envs/py3k/bin:" + os.environ.get("PATH")
     else:
         # else we're running locally and can use local settings
         build_tool = "sbt"
-        hadoop_version = os.environ.get("HADOOP_PROFILE", "hadoop2.3")
+        hadoop_version = os.environ.get("HADOOP_PROFILE", "hadoop2.6")
         test_env = "local"
 
     print("[info] Using build tool", build_tool, "with Hadoop profile", hadoop_version,