device: Avoid autoconnecting veths with wildcard connections

Don't auto connect connections without interfaces specified on software
links. This prevents the connections the user created for actual ethernet
devices to attach to veths but still leaves the user with possibility of
creating a connection specifically for that device.
Revert "core: make veth devices default-unmanaged for now"

veth devices being default unmanages makes it impossible to configure the
connectivity by NM on container bootup. Now that we don't add a default
connection when a veth is discovered is shouldn't be necessary to prevent
management anymore.

This reverts commit ebeaeaed4d3180c27cc059fe0ff199153fa9ec24.
Merge remote-tracking branches 'fd/lr/ipv6-tokens', 'fd/lr/nm-1-0-fixes', 'fd/lr/unmanaged-slaves', 'fd/lr/device-activation' and 'fd/lr/veth-managed' into integration