Removed writing 'vlan' from parameter string

[arthemis95]

Basically just removing the vlan parameter from the qemu arguments since it's depreciated. I did only change actually putting it in the string, the gui doesn't reflect the changes.

[TBK]

@pcwizzy37 completely removes vlan with this commit pcwizzy37@37d5447

[tobimensch]

I would accept a patch that fixes the GUI and all issues associated with the removal of vlan. There has to be an alternative way of doing those things, or QEMU wouldn't remove that feature, I'd think.

[jake01756]

How many people would use the vlan replacement? I don't. In issue #58 (comment) might contain the answer for a replacement.

I found out this commit, which removes the vlan parameter:
qemu/qemu@af1a5c3

the commit message says...

...should have
been enough time for everybody to either just drop unnecessary "vlan=0"
parameters, to switch to the modern -device + -netdev syntax for connecting
guest NICs with host network backends, or to switch to the "hubport" netdev
in case hubs are really wanted instead.

So how hard would it be to implement a replacement to fix this issue? To me it doesn't seem that hard but, things always seem easier than they are to me.