For CDH5.x version the spark service that is bundled with the CDH parcel was spark 1.6 version hence there was a need to add Spark2 as a separate parcel.
You need not add spark2 separately for CDH6.2. When you just add spark service in CDH6.2, it will install spark2.4.0 -- For your reference, This link contains the individual service packaged inside cdh6.2.x https://docs.cloudera.com/documentation/enterprise/6/release-notes/topics/rg_cdh_62_packaging.html#c...
If you would like to validate the version of spark installed alternatively you can run spark-shell --> This will show the spark version like this
Spark session available as 'spark'.
/ __/__ ___ _____/ /__
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/___/ .__/\_,_/_/ /_/\_\ version 2.4.0-cdh6.3.3
Using Scala version 2.11.12 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_141)
Type in expressions to have them evaluated.