Fix checkstyle paths

Change-Id: Ic5917b049da52127695e3f1a623d5f8aa73ddd5b
Reviewed-on: http://naan.mimuw.edu.pl:8001/74
Tested-by: Nebulostore Nebulostore <nebulostore@gmail.com>
Reviewed-by: Szymon Matejczyk <smatejczyk@gmail.com>