[SPARK-4990][Deploy]to find default properties file, search SPARK_CONF_DIR first

https://issues.apache.org/jira/browse/SPARK-4990

Author: WangTaoTheTonic <barneystinson@aliyun.com>
Author: WangTao <barneystinson@aliyun.com>

Closes #3823 from WangTaoTheTonic/SPARK-4990 and squashes the following commits:

133c43e [WangTao] Update spark-submit2.cmd
b1ab402 [WangTao] Update spark-submit
4cc7f34 [WangTaoTheTonic] rebase
55300bc [WangTaoTheTonic] use export to make it global
d8d3cb7 [WangTaoTheTonic] remove blank line
07b9ebf [WangTaoTheTonic] check SPARK_CONF_DIR instead of checking properties file
c5a85eb [WangTaoTheTonic] to find default properties file, search SPARK_CONF_DIR first

bin/spark-submit

@@ -44,7 +44,10 @@ while (($#)); do
   shift
 done
 
-DEFAULT_PROPERTIES_FILE="$SPARK_HOME/conf/spark-defaults.conf"
+if [ -z "$SPARK_CONF_DIR" ]; then
+  export SPARK_CONF_DIR="$SPARK_HOME/conf"
+fi
+DEFAULT_PROPERTIES_FILE="$SPARK_CONF_DIR/spark-defaults.conf"
 if [ "$MASTER" == "yarn-cluster" ]; then
   SPARK_SUBMIT_DEPLOY_MODE=cluster
 fi

bin/spark-submit2.cmd

@@ -24,7 +24,11 @@ set ORIG_ARGS=%*
 
 rem Reset the values of all variables used
 set SPARK_SUBMIT_DEPLOY_MODE=client
-set SPARK_SUBMIT_PROPERTIES_FILE=%SPARK_HOME%\conf\spark-defaults.conf
+
+if not defined %SPARK_CONF_DIR% (
+  set SPARK_CONF_DIR=%SPARK_HOME%\conf
+)
+set SPARK_SUBMIT_PROPERTIES_FILE=%SPARK_CONF_DIR%\spark-defaults.conf
 set SPARK_SUBMIT_DRIVER_MEMORY=
 set SPARK_SUBMIT_LIBRARY_PATH=
 set SPARK_SUBMIT_CLASSPATH=