Security update for gdm (moderate)

This update for gdm provides the following fixes:

This security issue was fixed:

• CVE-2018-14424: The daemon in GDM did not properly unexport display
  objects from its D-Bus interface when they are destroyed, which allowed
  a local attacker to trigger a use-after-free via a specially crafted
  sequence of D-Bus method calls, resulting in a denial of service or
  potential code execution (bsc#1103737)

These non-security issues were fixed:

• Enable pam_keyinit module (bsc#1081947)
• Fix a build race in SLE (bsc#1103093)

This update was imported from the SUSE:SLE-15:Update update project.