Hide 'Image Size' from install screen when installing in /data
calculating free size of internal storage from '/data' and not '/data/debian'

When lildebi is installed first time on a device, then /data/debian folder is not present. So when
the install screen (of installing in internal storage) tries to calculate the free size of internal storage
from /data/debian then an exception is generated as /data/debian is not present.
So instead of calculating free size from /data/debian, we will now calculate it from /data
use canonical/absolute path when finding free bytes on install path

The SD Card aka "external storage" on Android can do weird stuff with the
path to support the multi-user stuff.  Using the canonical path seems to
help with some of the issues, and if that fails, then try the absolute path.