[SPARK-4161]Spark shell class path is not correctly set if...

[SPARK-4161]Spark shell class path is not correctly set if "spark.driver.extraClassPath" is set in defaults.conf

Author: GuoQiang Li <witgo@qq.com>

Closes #3050 from witgo/SPARK-4161 and squashes the following commits:

abb6fa4 [GuoQiang Li] move usejavacp opt to spark-shell
89e39e7 [GuoQiang Li] review commit
c2a6f04 [GuoQiang Li] Spark shell class path is not correctly set if "spark.driver.extraClassPath" is set in defaults.conf

bin/spark-shell

@@ -45,6 +45,13 @@ source "$FWDIR"/bin/utils.sh
 SUBMIT_USAGE_FUNCTION=usage
 gatherSparkSubmitOpts "$@"
 
+# SPARK-4161: scala does not assume use of the java classpath,
+# so we need to add the "-Dscala.usejavacp=true" flag mnually. We
+# do this specifically for the Spark shell because the scala REPL
+# has its own class loader, and any additional classpath specified
+# through spark.driver.extraClassPath is not automatically propagated.
+SPARK_SUBMIT_OPTS="$SPARK_SUBMIT_OPTS -Dscala.usejavacp=true"
+
 function main() {
   if $cygwin; then
     # Workaround for issue involving JLine and Cygwin