Please review: [389 Project] #345: db deadlock return should not log error

[Noriko Hosoi]

https://fedorahosted.org/389/ticket/345

https://fedorahosted.org/389/attachment/ticket/345/0001-Ticket-345-db-deadlo...

Fix description: error log level is set to SLAPI_LOG_TRACE if
  DB_LOCK_DEADLOCK is returned from the BDB operations, otherwise
  set to SLAPI_LOG_FATAL.