iov address internally through realloc(3). However, since the function
parameter wasn't designed to allow the modified iov being passed back to
the caller, we ended up feeding iov with several corrupted entries(this
depends on how many arguments were pushed into iovec before set_charset())
to nmount(2).
This commit fixes this regression introduced in rev1.37 such that
mount_msdosfs(8) with code page conversion option(-W,-D) enabled works again.
Reviewed by: rodrigc
664df13033