ZEPPELIN-383 Override classpath with ZEPPELIN_CLASSPATH_OVERRIDES

Prepend ZEPPELIN_CLASSPATH_OVERRIDES environment variable when building CLASSPATH in the shell scripts.

This PR replaces the closed  ZEPL#398 and #386 - Sorry for the mess...

Author: Eric Charles <eric@datalayer.io>

Closes #412 from echarles/ZEPPELIN-383-CLASSPATH_OVERRIDES and squashes the following commits:

8572ec5 [Eric Charles] Use ZEPPELIN_CLASSPATH_OVERRIDES instead of CLASSPATH_OVERRIDES
d63cc55 [Eric Charles] Prepend CLASSPATH_OVERRIDES environment variable when building CLASSPATH in the shell scripts

bin/interpreter.sh

@@ -121,9 +121,9 @@ fi
 CLASSPATH+=":${ZEPPELIN_CLASSPATH}"
 
 if [[ -n "${SPARK_SUBMIT}" ]]; then
-    ${SPARK_SUBMIT} --class ${ZEPPELIN_SERVER} --driver-class-path "${CLASSPATH}" --driver-java-options "${JAVA_INTP_OPTS}" ${SPARK_SUBMIT_OPTIONS} ${SPARK_APP_JAR} ${PORT} &
+    ${SPARK_SUBMIT} --class ${ZEPPELIN_SERVER} --driver-class-path "${ZEPPELIN_CLASSPATH_OVERRIDESS}:${CLASSPATH}" --driver-java-options "${JAVA_INTP_OPTS}" ${SPARK_SUBMIT_OPTIONS} ${SPARK_APP_JAR} ${PORT} &
 else
-    ${ZEPPELIN_RUNNER} ${JAVA_INTP_OPTS} -cp ${CLASSPATH} ${ZEPPELIN_SERVER} ${PORT} &
+    ${ZEPPELIN_RUNNER} ${JAVA_INTP_OPTS} -cp ${ZEPPELIN_CLASSPATH_OVERRIDESS}:${CLASSPATH} ${ZEPPELIN_SERVER} ${PORT} &
 fi
 
 pid=$!

bin/zeppelin-daemon.sh

@@ -169,7 +169,7 @@ function start() {
 
   initialize_default_directories
 
-  nohup nice -n $ZEPPELIN_NICENESS $ZEPPELIN_RUNNER $JAVA_OPTS -cp $CLASSPATH $ZEPPELIN_MAIN >> "${ZEPPELIN_OUTFILE}" 2>&1 < /dev/null &
+  nohup nice -n $ZEPPELIN_NICENESS $ZEPPELIN_RUNNER $JAVA_OPTS -cp $ZEPPELIN_CLASSPATH_OVERRIDES:$CLASSPATH $ZEPPELIN_MAIN >> "${ZEPPELIN_OUTFILE}" 2>&1 < /dev/null &
   pid=$!
   if [[ -z "${pid}" ]]; then
     action_msg "${ZEPPELIN_NAME} start" "${SET_ERROR}"

bin/zeppelin.sh

@@ -85,4 +85,4 @@ if [[ ! -d "${ZEPPELIN_NOTEBOOK_DIR}" ]]; then
   $(mkdir -p "${ZEPPELIN_NOTEBOOK_DIR}")
 fi
 
-$(exec $ZEPPELIN_RUNNER $JAVA_OPTS -cp $CLASSPATH $ZEPPELIN_SERVER "$@")
+$(exec $ZEPPELIN_RUNNER $JAVA_OPTS -cp $ZEPPELIN_CLASSPATH_OVERRIDES:$CLASSPATH $ZEPPELIN_SERVER "$@")