rc.d/zpool: change mountcritlocal dep from BEFORE to REQUIRE

In cases where the `/boot` directory is mounted from a different disk,
`/boot/zfs/zpool.cache` will not be found during a `rc.d/zpool`
run. This is because `/etc/fstab` mounts are mounted in
`rc.d/mountcritlocal`, which currently runs AFTER (i.e. `REQUIRE:`)
`rc.d/zpool`.

This change swaps the `rcorder` of `rc.d/zpool`'s dependency on
`mountcritlocal` from `BEFORE:` to `REQUIRE:`. This will ensure that
`/boot` (or even `/etc/` in some configurations) to be visible while
searching for `zpool.cache`.

Reviewed by: imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/1614
Closes: https://github.com/freebsd/freebsd-src/pull/1614

libexec/rc/rc.d/zpool

@@ -3,8 +3,7 @@
 #
 
 # PROVIDE: zpool
-# REQUIRE: hostid disks
-# BEFORE: mountcritlocal
+# REQUIRE: hostid disks mountcritlocal
 # KEYWORD: nojail
 
 . /etc/rc.subr