Default metadata directory

[denkv]

Using the default metadata directory leads to exceptions.

Reproducability

Steps to reproduce the behavior:

1. Start the platform controller
2. Check logs
3. See this:

INFO [org.hobbit.controller.PlatformController] - <Platform has version 2.0.16>
INFO [org.hobbit.controller.docker.ContainerManagerImpl] - <Deployed as "production".>
INFO [org.hobbit.controller.PlatformController] - <Using default directory for local metadata.>
ERROR [org.hobbit.controller.docker.FileBasedImageManager] - <Exception while reading >
    | java.lang.IllegalArgumentException: Parameter 'directory' is not a directory: metadata
    |   at org.apache.commons.io.FileUtils.validateListFilesParameters(FileUtils.java:2629)
    |   at org.apache.commons.io.FileUtils.innerListFilesOrDirectories(FileUtils.java:1543)
    |   at org.apache.commons.io.FileUtils.listFiles(FileUtils.java:1876)
    |   at org.apache.commons.io.FileUtils.listFiles(FileUtils.java:1899)
    |   at org.hobbit.controller.docker.FileBasedImageManager$1.run(FileBasedImageManager.java:70)
    |   at java.base/java.util.TimerThread.mainLoop(Timer.java:556)
    |   at java.base/java.util.TimerThread.run(Timer.java:506)