Security update for libzypp, zypper (important)

The Software Update Stack was updated to receive fixes and enhancements.

libzypp:

Security issues fixed:

• CVE-2017-7435, CVE-2017-7436, CVE-2017-9269: Fix GPG check workflows,
  mainly for unsigned repositories and packages. (bsc#1045735, bsc#1038984)

Bug fixes:

• Re-probe on refresh if the repository type changes. (bsc#1048315)
• Propagate proper error code to DownloadProgressReport. (bsc#1047785)
• Allow to trigger an appdata refresh unconditionally. (bsc#1009745)
• Support custom repo variables defined in /etc/zypp/vars.d.
• Adapt loop mounting of ISO images. (bsc#1038132, bsc#1033236)
• Fix potential crash if repository has no baseurl. (bsc#1043218)

zypper:

• Adapt download callback to report and handle unsigned packages.
  (bsc#1038984)
• Report missing/optional files as ‘not found’ rather than ‘error’.
  (bsc#1047785)
• Document support for custom repository variables defined in
  /etc/zypp/vars.d.
• Emphasize that it depends on how fast PackageKit will respond to a
  ‘quit’ request sent if PK blocks package management.