zfs_putpages: actually update mtime and ctime

Reported by:	Paul Koch <paul.koch@akips.com>
Tested by:	Paul Koch <paul.koch@akips.com>
MFC after:	2 weeks


git-svn-id: svn+ssh://svn.freebsd.org/base/head@275401 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f