treewide: add explicit default variant

treewide: add explicit default variant

Some packages with variants did not specify the default among the
alternatives, so were left without any apk 'provider_priority'
for that package.  This caused the apk solver to select the wrong
variant, silently changing the requested package list.

Notable among these were busybox, procd and the hostapd/wpad suite.
This behavior presented in the imagebuilders when creating the
image as follows, silently replacing packages even when explicitly
requested:

    $ make image PACKAGES=busybox
    ...
    ( 14/148) Installing busybox-selinux (1.37.0-r6)
    ...

We add 'DEFAULT_VARIANT:=1' to the packages that were missing one,
providing apk with sufficient information to choose the correct
package.

See link below for further examples and discussion.

Link: https://github.com/openwrt/openwrt/pull/21288#issuecomment-3704101422
Signed-off-by: Eric Fahlgren <ericfahlgren@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/21358
(cherry picked from commit f4fdb9964a1add146e0efdeba864a6478212a9fa)
Link: https://github.com/openwrt/openwrt/pull/21355
Signed-off-by: Robert Marko <robimarko@gmail.com>