update docker-file

while it did not work out to depend in the health status of mysql for the start of kopano-server, its nevertheless an interesting value. since the dockerfile does not include an automatic healcheak, add it to the compose file.

Signed-off-by: Felix Bartels <felix@host-consultants.de>

docker-compose.yml-example

@@ -79,6 +79,11 @@ services:
       - MYSQL_PASSWORD=YOUR_PASSWORD #change here
       - MYSQL_DATABASE=kopano
       - MYSQL_USER=kopano
+    healthcheck:
+      test: ["CMD-SHELL", 'mysql --database=$$MYSQL_DATABASE --password=$$MYSQL_ROOT_PASSWORD --execute="SELECT count(table_name) > 0 FROM information_schema.tables;" --skip-column-names -B']
+      interval: 30s
+      timeout: 10s
+      retries: 4
     networks:
       - kopanonet
   
@@ -111,7 +116,8 @@ services:
     links:
       - db
     depends_on:
-      - "kssl"
+      - db
+      - kssl
     environment:
       - SERVICE_TO_START=server
       - TZ=Europe/Berlin