Revert "fixes livy_service_start() when spark_version is specified but livy version is not"
Revert "fixes livy_service_start() when spark_version is specified but livy version is not"

This reverts commit 010a52f14f48445d4b6bf8c91770a0a541cc734b.

rstudio/sparklyr,kevinykuo/sparklyr,kevinykuo/sparklyr,kevinykuo/sparklyr,rstudio/sparklyr,kevinykuo/sparklyr,rstudio/sparklyr,rstudio/sparklyr