Security update for xen (important)

This update for xen fixes the following issues:

Security issues fixed:

• CVE-2018-18849: Fixed an out of bounds memory access issue was found in
  the LSI53C895A SCSI Host Bus Adapter emulation while writing a message
  in lsi_do_msgin (bsc#1114423).
• CVE-2018-18883: Fixed a NULL pointer dereference that could have been
  triggered by nested VT-x that where not properly restricted
  (XSA-278)(bsc#1114405).
• CVE-2018-19965: Fixed denial of service issue from attempting to use
  INVPCID with a non-canonical addresses (XSA-279)(bsc#1115045).
• CVE-2018-19966: Fixed issue introduced by XSA-240 that could have caused
  conflicts with shadow paging (XSA-280)(bsc#1115047).
• CVE-2018-19961 CVE-2018-19962: Fixed insufficient TLB flushing /
  improper large page mappings with AMD IOMMUs (XSA-275)(bsc#1115040).

Non-security issues fixed:

• Added upstream bug fixes (bsc#1027519).

This update was imported from the SUSE:SLE-12-SP3:Update update project.