[SPARK-2894] spark-shell doesn't accept flags

As @sryza reported, spark-shell doesn't accept any flags.
The root cause is wrong usage of spark-submit in spark-shell and it come to the surface by #1801
Actually double quotes should be sufficient here, since it preserves whitespaces by default. The only reason why we needed the special handling for pyspark is that we need to pass the string literal in as an environment variable, otherwise python won't know how to split our arguments. We don't need to do the same here because this is already split by bash.