Make ufs_dirhashreclaimperc a percentage for real and
rename it to ufs_dirhashreclaimpercent, as suggested
by jhb@. As an added bonus this avoids divide-by-zero
errors.

Requested by:	jhb, markj
Reviewied by:	jhb, markj


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274834 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f