tui: fix interface sort order

tui: fix interface sort order

Currently, when multiple NICs are present in a system the TUI
sometimes selects the wrong interface (not the one that has the
default gateway/dhcp lease)

I assume this is due to HashMap's values yielding an iterator in
arbitrary order

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Co-authored-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
 [ TL: avoid intermediate vector, reuse the SelectView's iter()]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>