SPARK-2332 [build] add exclusion for old servlet-api on hadoop-client in core

Fix for class of test suite failures in jenkins

Author: Peter MacKinnon <pmackinn@redhat.com>

Closes #1271 from pdmack/master and squashes the following commits:

cfe59fd [Peter MacKinnon] exclude servlet-api in hadoop-client for sbt
6f39fec [Peter MacKinnon] add exclusion for old servlet-api on hadoop-client in core

core/pom.xml

@@ -34,6 +34,12 @@
     <dependency>
       <groupId>org.apache.hadoop</groupId>
       <artifactId>hadoop-client</artifactId>
+      <exclusions>
+        <exclusion>
+          <groupId>javax.servlet</groupId>
+          <artifactId>servlet-api</artifactId>
+        </exclusion>
+      </exclusions>
     </dependency>
     <dependency>
       <groupId>net.java.dev.jets3t</groupId>

project/SparkBuild.scala

@@ -371,7 +371,7 @@ object SparkBuild extends Build {
         "net.java.dev.jets3t"        % "jets3t"           % jets3tVersion excludeAll(excludeCommonsLogging),
         "commons-codec"              % "commons-codec"    % "1.5", // Prevent jets3t from including the older version of commons-codec
         "org.apache.derby"           % "derby"            % "10.4.2.0"                     % "test",
-        "org.apache.hadoop"          % hadoopClient       % hadoopVersion excludeAll(excludeJBossNetty, excludeAsm, excludeCommonsLogging, excludeSLF4J, excludeOldAsm),
+        "org.apache.hadoop"          % hadoopClient       % hadoopVersion excludeAll(excludeJBossNetty, excludeAsm, excludeCommonsLogging, excludeSLF4J, excludeOldAsm, excludeServletApi),
         "org.apache.curator"         % "curator-recipes"  % "2.4.0" excludeAll(excludeJBossNetty),
         "com.codahale.metrics"       % "metrics-core"     % codahaleMetricsVersion,
         "com.codahale.metrics"       % "metrics-jvm"      % codahaleMetricsVersion,