don't update ve config if not needed in get_vnc_console

Update ve config in get_vnc_console only if we changed vnc config.
updated URL to how to after moving repo under Parallels account
try to get VNC port several times

Sometimes dispatcher returns 0 as vnc port just after
enabling it. To workaround this bug let's try to get it
several times.
add support of networking in VMs

We can't add devices to running VMs, so let's add
method setup_dev to vif driver, wchi will add device.
And call it before instance start.
Merge branch 'master' of test-vm:pcs-nova-driver