docker: symlink fixes (#4747)

* Prevent circular links (symlinks) from being created:
	* /data/gogs/log/log -> /data/gogs/log
	* /data/gogs/data/data -> /data/gogs/data
	* /data/git/git -> /data/git

docker/s6/gogs/setup

@@ -13,11 +13,11 @@ fi
 cd /app/gogs
 
 # Link volumed data with app data
-ln -sf /data/gogs/log  ./log
+ln -sfn /data/gogs/log  ./log
-ln -sf /data/gogs/data ./data
+ln -sfn /data/gogs/data ./data
 
 # Backward Compatibility with Gogs Container v0.6.15
-ln -sf /data/git /home/git
+ln -sfn /data/git /home/git
 
 chown -R git:git /data /app/gogs ~git/
 chmod 0755 /data /data/gogs ~git/