Fix JRuby binary operator warning (#2352)
Fix JRuby binary operator warning (#2352)

Fixes the following warning shown by JRuby 9.1.6.0:

> gems/paperclip-5.1.0/lib/paperclip/storage/filesystem.rb:49: warning: `&' after local variable or literal is interpreted as binary operator even though it seems like argument prefix
gfvcastro/paperclip,gfvcastro/paperclip