[MINOR] Only rename SparkR tar.gz if names mismatch
[MINOR] Only rename SparkR tar.gz if names mismatch

## What changes were proposed in this pull request?

For release builds the R_PACKAGE_VERSION and VERSION are the same (e.g., 2.1.0). Thus `cp` throws an error which causes the build to fail.

## How was this patch tested?

Manually by executing the following script
```
set -o pipefail
set -e
set -x

touch a

R_PACKAGE_VERSION=2.1.0
VERSION=2.1.0

if [ "$R_PACKAGE_VERSION" != "$VERSION" ]; then
  cp a a
fi
```

Author: Shivaram Venkataraman <shivaram@cs.berkeley.edu>

Closes #16299 from shivaram/sparkr-cp-fix.

(cherry picked from commit 9634018c4d6d5a4f2c909f7227d91e637107b7f4)
Signed-off-by: Reynold Xin <c9d35a384bc579d1c6c8c055f2a2b5c04e11b521@databricks.com>

kimoonkim/spark,huang1900/spark,huang1900/spark,big-pegasus/spark,kimoonkim/spark,SnappyDataInc/spark,metamx/spark,ibm-research-ireland/sparkoscope,metamx/spark,ibm-research-ireland/sparkoscope,Panos-Bletsos/spark-cost-model-optimizer,kimoonkim/spark,huang1900/spark,huang1900/spark,Panos-Bletsos/spark-cost-model-optimizer,big-pegasus/spark,Panos-Bletsos/spark-cost-model-optimizer,Panos-Bletsos/spark-cost-model-optimizer,ibm-research-ireland/sparkoscope,SnappyDataInc/spark,huang1900/spark,huang1900/spark,ibm-research-ireland/sparkoscope,kimoonkim/spark,big-pegasus/spark,big-pegasus/spark,ibm-research-ireland/sparkoscope,Panos-Bletsos/spark-cost-model-optimizer,metamx/spark,SnappyDataInc/spark,big-pegasus/spark,kimoonkim/spark,metamx/spark,big-pegasus/spark,Panos-Bletsos/spark-cost-model-optimizer,SnappyDataInc/spark,kimoonkim/spark,SnappyDataInc/spark,SnappyDataInc/spark,Panos-Bletsos/spark-cost-model-optimizer,metamx/spark,SnappyDataInc/spark,ibm-research-ireland/sparkoscope,kimoonkim/spark,big-pegasus/spark,huang1900/spark,ibm-research-ireland/sparkoscope,metamx/spark,metamx/spark