Track down Contexts without data directories.

Data directories for all packages should be created and managed by
installd; if we create a Context and the data directory doesn't exist
yet, we're in trouble, since a later mkdirs() would end up creating
the directory with incorrect permissions, mode, and SELinux labels.

Bug: 28272737
Change-Id: Ie3bb884ab07748719378de5c792046a031a3f945