i386: Change the default Hyper-V version to match WS2016

i386: Change the default Hyper-V version to match WS2016

KVM implements some Hyper-V 2016 functions so providing WS2008R2 version
is somewhat incorrect. While generally guests shouldn't care about it
and always check feature bits, it is known that some tools in Windows
actually check version info.

For compatibility reasons make the change for 6.2 machine types only.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20210902093530.345756-9-vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>