fix spark_write_table from append regression and db_save_query
fix spark_write_table from append regression and db_save_query

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