Change snap to previous MongoDB version 3.2.18 because of data loss:

https://github.com/wekan/wekan-mongodb/issues/9

snapcraft.yaml

@@ -65,7 +65,7 @@ apps:
 
 parts:
     mongodb:
-        source: https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-ubuntu1604-3.2.19.tgz
+        source: https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-ubuntu1604-3.2.18.tgz
         plugin: dump
         stage-packages: [libssl1.0.0]
         filesets: