Remove -m (update) from ldconfig -32 & -soft invocation on startup.

Since r154114 which introduced ldconfig_local32_dirs, ldconfig -32 was
called with -m. This means that ld-elf32.so.hints paths set is not
cleared for compat32 on boot, unlike ld,so,hints. Same -m was used in
r294295 for ld-elf-soft.so.hints on arm. The patch fixes the
asymmetry.

Noted by: Andreas Longwitz <longwitz@incore.de>
Reviewed by: brooks, emaste, imp
Discussed with: bdrewery
Sponsored by: The FreeBSD Foundation
Approved by: re (gjb)
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D17331