image.bbclass: create device table after package installation
Now that the makedevs supports using user/group names in the devcie
table files, and it uses passwd and group files under the rootfs which
is provided by the base-passwd package, we should let package installation
finish first, so that makedevs can get a correct mapping from user/group
names to uid/gid.
The check for existence of ${IMAGE_ROOTFS}/dev is removed. This is because
do_rootfs doesn't have 'nostamp' flag any more, so the do_rootfs task will
not be rerun for every build. Checking for the existence of ${IMAGE_ROOTFS}/dev
is not necessary any more. Besides, as base-files package also installs the
/dev directory, this checking does not serve as a good criteria.
