Fix file handle leak

Author: wchen-r7

modules/auxiliary/scanner/http/http_traversal.rb

@@ -332,10 +332,7 @@ def is_writable(trigger)
   # This is used in the lfi_download() function
   #
   def load_filelist
-    f = File.open(datastore['FILELIST'], 'rb')
-    buf = f.read
-    f.close
-    return buf
+    File.open(datastore['FILELIST'], 'rb') {|f| buf = f.read}
   end
 
   def run_host(ip)