[SPARK-2118] spark class should complain if tools jar is missing.

Author: Prashant Sharma <prashant.s@imaginea.com>

Closes #1068 from ScrapCodes/SPARK-2118/tools-jar-check and squashes the following commits:

29e768b [Prashant Sharma] Code Review
5cb6f7d [Prashant Sharma] [SPARK-2118] spark class should complaing if tools jar is missing.

bin/spark-class

@@ -130,6 +130,11 @@ else
 fi
 
 if [[ "$1" =~ org.apache.spark.tools.* ]]; then
+  if test -z "$SPARK_TOOLS_JAR"; then
+    echo "Failed to find Spark Tools Jar in $FWDIR/tools/target/scala-$SCALA_VERSION/" 1>&2
+    echo "You need to build spark before running $1." 1>&2
+    exit 1
+  fi
   CLASSPATH="$CLASSPATH:$SPARK_TOOLS_JAR"
 fi