detect-filename: avoid multiple inspections of buf

If the filename inspection function is returning nomatch this will
trigger iterative inspections with same content (aka filename) being
inspected. To avoid this we change the return as the buffer inspection
has not to be inspected anymore.

src/detect-filename.c

@@ -418,7 +418,7 @@ static int DetectEngineInspectFilename(
     if (r == 1)
         return DETECT_ENGINE_INSPECT_SIG_MATCH;
     else
-        return DETECT_ENGINE_INSPECT_SIG_NO_MATCH;
+        return DETECT_ENGINE_INSPECT_SIG_CANT_MATCH_FILESTORE;
 }
 
 typedef struct PrefilterMpmFilename {