[SPARK-11538][BUILD] Force guava 14 in sbt build.

sbt's version resolution code always picks the most recent version, and we
don't want that for guava.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #9508 from vanzin/SPARK-11538.

project/SparkBuild.scala

@@ -207,7 +207,8 @@ object SparkBuild extends PomBuild {
   // Note ordering of these settings matter.
   /* Enable shared settings on all projects */
   (allProjects ++ optionallyEnabledProjects ++ assemblyProjects ++ Seq(spark, tools))
-    .foreach(enable(sharedSettings ++ ExcludedDependencies.settings ++ Revolver.settings))
+    .foreach(enable(sharedSettings ++ DependencyOverrides.settings ++
+      ExcludedDependencies.settings ++ Revolver.settings))
 
   /* Enable tests settings for all projects except examples, assembly and tools */
   (allProjects ++ optionallyEnabledProjects).foreach(enable(TestSettings.settings))
@@ -291,6 +292,14 @@ object Flume {
   lazy val settings = sbtavro.SbtAvro.avroSettings
 }
 
+/**
+ * Overrides to work around sbt's dependency resolution being different from Maven's.
+ */
+object DependencyOverrides {
+  lazy val settings = Seq(
+    dependencyOverrides += "com.google.guava" % "guava" % "14.0.1")
+}
+
 /**
   This excludes library dependencies in sbt, which are specified in maven but are
   not needed by sbt build.