Pick NEXT_MIN libvirt/QEMU versions for "V" release

The last time we incremented versions for libvirt and QEMU was during
the "Stein" release[1].  For "Train" we didn't do any (although we
advertized).  The advertized NEXT_MIN_{LIBVIRT,QEMU} versions for
"Train" release were set to: libvirt 4.0.0 and QEMU 2.11.0; but we
actually didn't bump them for "Train"; we'll do that for "Ussuri".

But before we bump for "Ussuri", we need to pick NEXT_MIN versions for
the "V" release.  Based on the LibvirtDistroSupportMatrix[3], this patch
announces a version increment for libvirt and QEMU that will be applied
for the "V" release, with predicted minimum versions setting:

    libvirt to 5.0.0; and
       QEMU to 4.0.0

[1] https://opendev.org/openstack/nova/commit/0b1548a988 -- libvirt:
    Bump MIN_{LIBVIRT,QEMU}_VERSION for "Stein", 2019-01-22
[2] https://opendev.org/openstack/nova/commit/0b1548a988 -- Pick next
    minimum libvirt / QEMU versions for "T" release
[3] https://wiki.openstack.org/wiki/LibvirtDistroSupportMatrix

Change-Id: I3d3679705dcfdd4b0ef058b40769e4c3811a1472
Signed-off-by: Kashyap Chamarthy <kchamart@redhat.com>

nova/virt/libvirt/driver.py

@@ -234,8 +234,8 @@ def repr_method(self):
 # MIN_LIBVIRT_VERSION can be updated to match this after
 # NEXT_MIN_LIBVIRT_VERSION  has been at a higher value for
 # one cycle
-NEXT_MIN_LIBVIRT_VERSION = (4, 0, 0)
-NEXT_MIN_QEMU_VERSION = (2, 11, 0)
+NEXT_MIN_LIBVIRT_VERSION = (5, 0, 0)
+NEXT_MIN_QEMU_VERSION = (4, 0, 0)
 
 
 # Virtuozzo driver support