MAPR-17422: Ensure only Spark log4j.properties is picked up.

When SPARK_CLASSPATH or SPARK_SUBMIT_CLASSPATH contains log4j.properties, they
will get picked up instead of Spark's version because they are present before
the Spark conf dir in classpath.

Testing:
Verified the INFO Messages don't get printed when the level is set to WARN.

bin/compute-classpath.cmd

@@ -36,14 +36,17 @@ rem Load environment variables from conf\spark-env.cmd, if it exists
 if exist "%FWDIR%conf\spark-env.cmd" call "%FWDIR%conf\spark-env.cmd"
 
 rem Build up classpath
-set CLASSPATH=%SPARK_CLASSPATH%;%SPARK_SUBMIT_CLASSPATH%
 
 if not "x%SPARK_CONF_DIR%"=="x" (
   set CLASSPATH=%CLASSPATH%;%SPARK_CONF_DIR%
 ) else (
   set CLASSPATH=%CLASSPATH%;%FWDIR%conf
 )
 
+rem Add the external jars after adding spark conf so that Spark's log4j.properties
+rem is picked up.
+set CLASSPATH=%CLASSPATH%;%SPARK_CLASSPATH%;%SPARK_SUBMIT_CLASSPATH%
+
 if exist "%FWDIR%RELEASE" (
   for %%d in ("%FWDIR%lib\spark-assembly*.jar") do (
     set ASSEMBLY_JAR=%%d

bin/compute-classpath.sh

@@ -37,16 +37,18 @@ function appendToClasspath(){
   fi
 }
 
-appendToClasspath "$SPARK_CLASSPATH"
-appendToClasspath "$SPARK_SUBMIT_CLASSPATH"
-
 # Build up classpath
 if [ -n "$SPARK_CONF_DIR" ]; then
   appendToClasspath "$SPARK_CONF_DIR"
 else
   appendToClasspath "$FWDIR/conf"
 fi
 
+# Add the external jars after adding spark conf so that Spark's log4j.properties
+appendToClasspath "$SPARK_CLASSPATH"
+appendToClasspath "$SPARK_SUBMIT_CLASSPATH"
+
+
 ASSEMBLY_DIR="$FWDIR/assembly/target/scala-$SPARK_SCALA_VERSION"
 
 if [ -n "$JAVA_HOME" ]; then