Security update for xen (important)

This update for xen to version 4.7.2 fixes the following issues:

These security issues were fixed:

• CVE-2017-7228: Broken check in memory_exchange() permited PV guest
  breakout (bsc#1030442).
• XSA-206: Unprivileged guests issuing writes to xenstore were able to
  stall progress of the control domain or driver domain, possibly leading
  to a Denial of Service (DoS) of the entire host (bsc#1030144).
• CVE-2017-6505: The ohci_service_ed_list function in hw/usb/hcd-ohci.c
  allowed local guest OS users to cause a denial of service (infinite
  loop) via vectors involving the number of link endpoint list descriptors
  (bsc#1028235).

These non-security issues were fixed:

• bsc#1015348: libvirtd didn’t not start during boot
• bsc#1014136: kdump couldn’t dump a kernel on SLES12-SP2 with Xen
  hypervisor.
• bsc#1026236: Fixed paravirtualized performance
• bsc#1022555: Timeout in "execution of /etc/xen/scripts/block add"
• bsc#1029827: Forward port xenstored
• bsc#1029128: Make xen to really produce xen.efi with gcc48

This update was imported from the SUSE:SLE-12-SP2:Update update project.