Network interface numbering starts from 1, therefore when accessing
help/index array, the interface index should not be used directly, but
rather decremented by 1, to avoid out-of-bound access on those arrays.
Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>
Allow multiple commands use the same dynamic shell command
completion when expecting network interface index.
For example "net iface" and "net stats" are such commands.
The network interface expansion cannot be used in "net ipv6 add",
"net ipv4 add" and "net route" commands as they require more
data after the network interface index argument.
Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>