qemu: fix removal of <interface type='hostdev'>

This patch (and the two patches that precede it) resolve:

  https://bugzilla.redhat.com/show_bug.cgi?id=1005682

When libvirt was changed to delay the final cleanup of device removal
until the qemu process had signaled it with a DEVICE_DELETED event for
that device, the hostdev removal function
(qemuDomainRemoveHostDevice()) was written to properly handle the
removal of a hostdev that was actually an SRIOV virtual function
(defined with <interface type='hostdev'>). However, the function used
to search for a device matching the alias name provided in the
DEVICE_DELETED message (virDomainDefFindDevice()) would search through
the list of netdevs before hostdevs, so qemuDomainRemoveHostDevice()
was never called; instead the netdev function,
qemuDomainRemoveNetDevice() (which *doesn't* properly cleanup after
removal of <interface type='hostdev'>), was called.

(As a reminder - each <interface type='hostdev'> results in a
virDomainNetDef which contains a virDomainHostdevDef having a parent
type of VIR_DOMAIN_DEVICE_NET, and parent.data.net pointing back to
the virDomainNetDef; both Defs point to the same device info object
(and the info contains the device's "alias", which is used by qemu to
identify the device). The virDomainHostdevDef is added to the domain's
hostdevs list *and* the virDomainNetDef is added to the domain's nets
list, so searching either list for a particular alias will yield a
positive result.)

This function modifies the qemuDomainRemoveNetDevice() to short
circuit itself and call qemu DomainRemoveHostDevice() instead when the
actual device is a VIR_DOMAIN_NET_TYPE_HOSTDEV (similar logic to what
is done in the higher level qemuDomainDetachNetDevice())

Note that even if virDomainDefFindDevice() changes in the future so
that it finds the hostdev entry first, the current code will continue
to work properly.

src/qemu/qemu_hotplug.c

@@ -2593,6 +2593,12 @@ qemuDomainRemoveNetDevice(virQEMUDriverPtr driver,
     virDomainEventPtr event;
     size_t i;
 
+    if (virDomainNetGetActualType(net) == VIR_DOMAIN_NET_TYPE_HOSTDEV) {
+        /* this function handles all hostdev and netdev cleanup */
+        qemuDomainRemoveHostDevice(driver, vm, virDomainNetGetActualHostdev(net));
+        return;
+    }
+
     VIR_DEBUG("Removing network interface %s from domain %p %s",
               net->info.alias, vm, vm->def->name);