[SPARK-18740] Log spark.app.name in driver logs

## What changes were proposed in this pull request?

Added simple logInfo line to print out the `spark.app.name` in the driver logs

## How was this patch tested?

Spark was built and tested with SparkPi app. Example log:
```
16/12/06 05:49:50 INFO spark.SparkContext: Running Spark version 2.0.0
16/12/06 05:49:52 INFO spark.SparkContext: Submitted application: Spark Pi
16/12/06 05:49:52 INFO spark.SecurityManager: Changing view acls to: root
16/12/06 05:49:52 INFO spark.SecurityManager: Changing modify acls to: root
```

Author: Peter Ableda <peter.ableda@cloudera.com>

Closes #16172 from peterableda/feature/print_appname.