Security update for net-snmp (important)

This update for net-snmp fixes the following issues:

Security issues fixed:

• CVE-2018-18065: _set_key in agent/helpers/table_container.c had a NULL
  Pointer Exception bug that can be used by an authenticated attacker to
  remotely cause the instance to crash via a crafted UDP packet, resulting
  in Denial of Service. (bsc#1111122)

Non-security issues fixed:

• swintst_rpm: Protect against unspecified Group name (bsc#1102775)
• Add tsm and tlstm MIBs and the USM security module. (bsc#1081164)
• Fix agentx freezing on timeout (bsc#1027353)

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