Commit 7e62c4cd (first appearing in libvirt-3.9.0 as a resolution
to rhbz #1343919) added a "generated" attribute to virMacAddr that was
set whenever a mac address was auto-generated by libvirt. This
knowledge was used in a single place - when trying to match a NetDef
from the Domain to Delete with user-provided XML. Since the XML parser
always auto-generates a MAC address for NetDefs when none is provided,
it was previously impossible to make a search where the MAC address
isn't significant, but the addition of the "generated" attribute made
it possible for the search function to ignore auto-generated MACs.

This implementation had a problem though - it was adding a field to a
"low level" struct - virMacAddr - which is used in other places with
the assumption that it contains exactly a 6 byte MAC address and
nothing else. In particular, virNWFilterSnoopEthHdr uses virMacAddr as
part of the definition of an ethernet packet header, whose layout must
of course match an actual ethernet packet. Adding the extra bools into
virNWFilterSnoopEthHdr caused the nwfilter driver's "IP discovery via
DHCP packet snooping" functionality to mysteriously stop working.

In order to fix that behavior, and prevent potential future similar
odd behavior, this patch moves the "generated" member out of
virMacAddr (so that it is again really is just a MAC address) into
virDomainNetDef, and sets it only when virDomainNetGenerateMAC() is
called from virDomainNetDefParseXML() (which is the only time we care
about it).

Resolves: https://bugzilla.redhat.com/1529338

(It should also be applied to any maintenance branch that applies
commit 7e62c4cd and friends to resolve
https://bugzilla.redhat.com/1343919)
Signed-off-by: NLaine Stump <laine@laine.org>