[BUG] VLAN removal isn't taking None/none reset value

[sadsfae]

Version tested: 2.0.5 but this is likely present in 2.1.0

We should be able to remove the VLAN association from an environment with --mod-cloud --cloud cloud0x --vlan none but it appears broken in 2.1

https://github.com/redhat-performance/quads?tab=readme-ov-file#creating-a-new-cloud-assignment-and-schedule

# quads --mod-cloud --cloud cloud60 --vlan none
Could not parse vlan id. Only integers accepted

We can't pass a null / empty value either as it doesn't take effect.

# quads --mod-cloud --cloud cloud60 --vlan ""
Cloud modified successfully

# quads --ls-vlan | grep cloud60
606: cloud60