[WebHCat] Complete implementation of webhcat endpoint "version/sqoop"

Since WebHCat support invoking Sqoop job (introduced in HIVE-5072), it should also expose endpoint "version/sqoop" to return the version of Sqoop interactive. In HIVE-5072, the endpoint "version/sqoop" is exposed return "NOT_IMPLEMENTED_501". The reason is we cannot simply do the same as the endpoint "version/hive" or "version/hadoop" since WebHCat does not have dependency with Sqoop. Currently Sqoop 1 support getting the version using command "sqoop version". WebHCat can invoke this command using "templeton/v1/sqoop" endpoint but this is not interactive.