[2/2] spark git commit: [Minor] [SQL] Cleans up DataFrame variable names and toDF() calls

[Minor] [SQL] Cleans up DataFrame variable names and toDF() calls Although we've migrated to the DataFrame API, lots of code still uses `rdd` or `srdd` as local variable names. This PR tries to address these naming inconsistencies and some other minor DataFrame related style issues. [https://r

[2/2] spark git commit: [Minor] [SQL] Cleans up DataFrame variable names and toDF() calls

[Minor] [SQL] Cleans up DataFrame variable names and toDF() calls Although we've migrated to the DataFrame API, lots of code still uses `rdd` or `srdd` as local variable names. This PR tries to address these naming inconsistencies and some other minor DataFrame related style issues. [https://r