vmx: allow an odd number of vCPUs

vmx: allow an odd number of vCPUs

Most probably this was a limitation in older ESX versions, and it seems
it does not exist anymore in more recent versions; see the following
thread:
https://www.redhat.com/archives/libvir-list/2018-May/msg02159.html
https://www.redhat.com/archives/libvir-list/2018-June/msg00043.html

Hence, allow an odd number (greater than 1) of vCPUs, since most
probably older versions of ESXi will error out anyway.

https://bugzilla.redhat.com/show_bug.cgi?id=1584091

Signed-off-by: Pino Toscano <ptoscano@redhat.com>
Reviewed-by: Jiri Denemark <jdenemar@redhat.com>