Xen-4.5.0-rc4: Update tag for qemu-xen.

QEMU-traditional has nothing new, so stay at rc1 there.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Merge tag '4.5.0-rc4' into staging

Xen 4.5.0 RC4