Don't show "DDL:set_token_filters" log when it's not needed
Don't show "DDL:set_token_filters" log when it's not needed

Not needed case:

  * Both the current token filters and new token filters are empty.

komainu8/groonga,hiroyuki-sato/groonga,redfigure/groonga,komainu8/groonga,kenhys/groonga,kenhys/groonga,redfigure/groonga,hiroyuki-sato/groonga,groonga/groonga,cosmo0920/groonga,komainu8/groonga,cosmo0920/groonga,hiroyuki-sato/groonga,redfigure/groonga,kenhys/groonga,kenhys/groonga,cosmo0920/groonga,naoa/groonga,groonga/groonga,cosmo0920/groonga,groonga/groonga,hiroyuki-sato/groonga,hiroyuki-sato/groonga,groonga/groonga,hiroyuki-sato/groonga,cosmo0920/groonga,komainu8/groonga,naoa/groonga,redfigure/groonga,naoa/groonga,groonga/groonga,naoa/groonga,hiroyuki-sato/groonga,naoa/groonga,kenhys/groonga,komainu8/groonga,redfigure/groonga,naoa/groonga,komainu8/groonga,naoa/groonga,redfigure/groonga,komainu8/groonga,hiroyuki-sato/groonga,cosmo0920/groonga,kenhys/groonga,kenhys/groonga,naoa/groonga,groonga/groonga,komainu8/groonga,groonga/groonga,cosmo0920/groonga,cosmo0920/groonga,redfigure/groonga,kenhys/groonga,groonga/groonga,redfigure/groonga