Fix a bug in the Aho-Corasick search.
Fix a bug in the Aho-Corasick search.

Fallback nodes were being set incorrectly because f was not being reset to 0.

unixabg/redwood,vishnuvaradaraj/redwood,yinheli/redwood-filter,unixabg/redwood,vishnuvaradaraj/redwood,andybalholm/redwood,yinheli/redwood-filter,yinheli/redwood-filter,andybalholm/redwood,vishnuvaradaraj/redwood