Correct File Storage to internal, fixes #6 (#218)

Signed-off-by: d067928 <jakob.moeller@sap.com>

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/storage/FileStorageHelper.kt

@@ -27,12 +27,10 @@ object FileStorageHelper {
      * Get key files export directory used to store all export files for the transaction
      * Uses FileStorageConstants.KEY_EXPORT_DIRECTORY_NAME constant
      *
-     * TODO Change to CacheDir before release
-     *
      * @return File of key export directory
      */
     val keyExportDirectory = File(
-        CoronaWarnApplication.getAppContext().getExternalFilesDir(null),
+        CoronaWarnApplication.getAppContext().cacheDir,
         FileStorageConstants.KEY_EXPORT_DIRECTORY_NAME
     )
 

Corona-Warn-App/src/main/java/de/rki/coronawarnapp/storage/keycache/KeyCacheRepository.kt

@@ -59,7 +59,8 @@ class KeyCacheRepository(private val keyCacheDao: KeyCacheDao) {
     )
 
     suspend fun deleteOutdatedEntries() = keyCacheDao.getAllEntries().forEach {
-        if (File(it.path).isOutdated()) {
+        val file = File(it.path)
+        if (file.isOutdated() || !file.exists()) {
             deleteFileForEntry(it)
             keyCacheDao.deleteEntry(it)
         }