Fix syslog log_level and tag prefix for swift

Use top scope for debug,verbose,syslog_log_level for swift as well.
Add swift- prefix for remote log file names

Signed-off-by: Bogdan Dobrelya <bogdando@mail.ru>
Merge pull request #338 from bogdando/fix_swiftsyslog

Fix syslog log_level and tag prefix for swift