cfg2cmd: use long form QEMU parameters to avoid warning in 6.0

cfg2cmd: use long form QEMU parameters to avoid warning in 6.0

QEMU warns us about this:

kvm: -chardev socket,id=qmp,path=/var/run/qemu-server/100.qmp,server,nowait: warning: short-form boolean option 'server' deprecated
Please use server=on instead
kvm: -chardev socket,id=qmp,path=/var/run/qemu-server/100.qmp,server,nowait: warning: short-form boolean option 'nowait' deprecated
Please use wait=off instead
kvm: -vnc unix:/var/run/qemu-server/100.vnc,password: warning: short-form boolean option 'password' deprecated
Please use password=on instead

The new syntax is backwards compatible to at least QEMU 4.0.

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>