802.1Qbg: use pre-associate state at beginning of inc. migr

802.1Qbg: use pre-associate state at beginning of inc. migr

This patch introduces the usage of the pre-associate state of the IEEE 802.1Qbg standard on incoming VM migration on the target host. It is in response to bugzilla entry 632750.

https://bugzilla.redhat.com/show_bug.cgi?id=632750

For being able to differentiate the exact reason as to why a macvtap device is being created, either due to a VM creation or an incoming VM migration, I needed to pass that reason as a parameter from wherever qemudStartVMDaemon is being called in order to determine whether to send an ASSOCIATE (VM creation) or a PRE-ASSOCIATE (incoming VM migration) towards lldpad.

I am also fixing a problem with the virsh domainxml-to-native call on the way.

Gerhard successfully tested the patch with a recent blade network 802.1Qbg-compliant switch.

The patch should not have any side-effects on the 802.1Qbh support in libvirt, but Roopa (cc'ed) may want to verify this.