Revert "App: only init the data store once per application."

It seems like this is the cause of #97 as 19b4e2a796
hasn't fixed the issue. Still not sure why it's happening, but reverting
it so no more users suffer from this issue.

This reverts commit 26ea8900a2.

app/src/main/java/com/etesync/syncadapter/App.kt

@@ -51,7 +51,8 @@ class App : Application() {
      * `@Provides @Singleton`.
      */
     // override onUpgrade to handle migrating to a new version
-    val data = initDataStore()
+    val data: MyEntityDataStore
+        get() = initDataStore()
 
     fun initDataStore(): MyEntityDataStore {
         val source = MyDatabaseSource(this, Models.DEFAULT, 4)