libnm-core: fail verify() for NMSettingVlan for invalid vlan id

libnm-core: fail verify() for NMSettingVlan for invalid vlan id

Point in case:

    # ip link add link dummy0 name dummy0.vlan type vlan id 4095
    RTNETLINK answers: Numerical result out of range

This potentially causes existing (invalid) connections to disappear
as they now fail verification.

Instead of adjusting the range of the GObject property
NM_SETTING_VLAN_ID, reject it during vlan. This is a bit more
forgiving to an older client that isn't aware of this new restriction,
so he can first set the value without raising a critical warning.