[Elastic Agent] Fix deb/rpm installation (elastic#22153)

* Fix issue on elastic-agent systemd unit.

* Fix service file for fedora.

* Add changelog.

(cherry picked from commit f07cc32)

dev-tools/packaging/templates/linux/elastic-agent.unit.tmpl

@@ -9,10 +9,8 @@ After=network-online.target
 User={{ .BeatUser }}
 Group={{ .BeatUser }}
 {{- end }}
-Environment="BEAT_LOG_OPTS="
 Environment="BEAT_CONFIG_OPTS=-c /etc/{{.BeatName}}/{{.BeatName}}.yml"
-Environment="BEAT_PATH_OPTS=--path.home /var/lib/{{.BeatName}} --path.config /etc/{{.BeatName}} --path.data /var/lib/{{.BeatName}}/data --path.logs /var/log/{{.BeatName}}"
-ExecStart=/usr/share/{{.BeatName}}/bin/{{.BeatName}} --environment systemd $BEAT_LOG_OPTS $BEAT_CONFIG_OPTS $BEAT_PATH_OPTS
+ExecStart=/usr/bin/{{.BeatName}} run --environment systemd $BEAT_CONFIG_OPTS
 Restart=always
 
 [Install]

x-pack/elastic-agent/CHANGELOG.next.asciidoc

@@ -23,6 +23,7 @@
 - Rename monitoring index from `elastic.agent` to `elastic_agent` {pull}21932[21932]
 - Fix missing elastic_agent event data {pull}21994[21994]
 - Ensure shell wrapper path exists before writing wrapper on install {pull}22144[22144]
+- Fix deb/rpm packaging for Elastic Agent {pull}22153[22153]
 
 ==== New features