horizon 18.4.0 release

meta:version: 18.4.0
meta:diff-start: -
meta:series: victoria
meta:release-type: release
meta:pypi: no
meta:first: yes
meta:release:Author: manchandavishal <manchandavishal143@gmail.com>
meta:release:Commit: manchandavishal <manchandavishal143@gmail.com>
meta:release:Change-Id: I51ceb971cf0155db29c3c08580feddd33b3c1356
meta:release:Code-Review+2: Sean McGinnis <sean.mcginnis@gmail.com>
meta:release:Workflow+1: Sean McGinnis <sean.mcginnis@gmail.com>