After having applied commit 9954e7af ("nilfs2: add free
entries count only if clear bit operation succeeded"), a free routine
of nilfs came to fall into an infinite loop, outputting the same
message endlessly:

 nilfs_palloc_freev: entry number 29497 already freed
 nilfs_palloc_freev: entry number 29497 already freed
 nilfs_palloc_freev: entry number 29497 already freed
 nilfs_palloc_freev: entry number 29497 already freed
 nilfs_palloc_freev: entry number 29497 already freed ...

That patch broke the routine so that a loop counter is never updated
in an abnormal state.  This fixes the regression.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>