Tweak docker compose setup (#11785)

* fix stray dockerhost mention

* fix stray whitespace

* fix missing mattermost-redix cleanup in clean-old-docker

* absolute path to docker-compose, plus simpler ldap initialization

* allow ldapadd to fail on CI

build/legacy.mk

@@ -56,3 +56,8 @@ clean-old-docker:
 		docker rm -v mattermost-elasticsearch > /dev/null; \
 	fi
 
+	@if [ $(shell docker ps -a | grep -ci mattermost-redis) -eq 1 ]; then \
+		echo removing mattermost-redis; \
+		docker stop mattermost-redis > /dev/null; \
+		docker rm -v mattermost-redis > /dev/null; \
+	fi