bug #2483: set cdrom disk type in xen driver

(cherry picked from commit 78233c496d7a6c112b13f290787aa1b3ad090a2a)
bug #2585: user proper vnc parameters for HVM XEN

(cherry picked from commit 3338cd039cb32d638481a09e5ddf6e585f92bd58)
Merge remote-tracking branch 'upstream/one-4.4' into one-4.4