Update run-example

Old code can only be ran under spark_home and use "bin/run-example".
 Error "./run-example: line 55: ./bin/spark-submit: No such file or directory" appears when running in other place. So change this

Author: maji2014 <maji3@asiainfo-linkage.com>

Closes apache#1011 from maji2014/master and squashes the following commits:

2cc1af6 [maji2014] Update run-example

Closes apache#988.
(cherry picked from commit e9261d0)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>

bin/run-example

@@ -51,7 +51,7 @@ if [[ ! $EXAMPLE_CLASS == org.apache.spark.examples* ]]; then
   EXAMPLE_CLASS="org.apache.spark.examples.$EXAMPLE_CLASS"
 fi
 
-./bin/spark-submit \
+"$FWDIR"/bin/spark-submit \
   --master $EXAMPLE_MASTER \
   --class $EXAMPLE_CLASS \
   "$SPARK_EXAMPLES_JAR" \