fix #3258: block vm start when pci device is already in use

fix #3258: block vm start when pci device is already in use

on vm start, we reserve all pciids that we use, and
remove the reservation again in vm_stop_cleanup

first with only a time-based reservation but after the vm is started,
we reserve again but with the pid.

for this, we have to move the start_timeout calculation above the
hostpci handling.

also moved the pci initialization out of the conf parsing loop
so that we can reserve all ids before we actually touch any of them

while touching the lines, fix the indentation

this way, when a vm starts with a pci device that is already configured
for a different running vm, will not be started and the user gets
the error that the device is already in use

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>