Revert Mesos version to 0.9 since the 0.12 artifact has target Java 7

project/SparkBuild.scala

@@ -178,7 +178,7 @@ object SparkBuild extends Build {
       "it.unimi.dsi" % "fastutil" % "6.4.4",
       "colt" % "colt" % "1.2.0",
       "net.liftweb" % "lift-json_2.9.2" % "2.5",
-      "org.apache.mesos" % "mesos" % "0.12.0-incubating",
+      "org.apache.mesos" % "mesos" % "0.9.0-incubating",
       "io.netty" % "netty-all" % "4.0.0.Beta2",
       "org.apache.derby" % "derby" % "10.4.2.0" % "test",
       "com.codahale.metrics" % "metrics-core" % "3.0.0",