[SPARK-13521][BUILD] Remove reference to Tachyon in cluster & release scripts

## What changes were proposed in this pull request?
We provide a very limited set of cluster management script in Spark for Tachyon, although Tachyon itself provides a much better version of it. Given now Spark users can simply use Tachyon as a normal file system and does not require extensive configurations, we can remove this management capabilities to simplify Spark bash scripts.

Note that this also reduces coupling between a 3rd party external system and Spark's release scripts, and would eliminate possibility for failures such as Tachyon being renamed or the tar balls being relocated.

## How was this patch tested?
N/A

Author: Reynold Xin <rxin@databricks.com>

Closes #11400 from rxin/release-script.