the select_parent method in RuntimeLchan currently implements a way
to escape from an application that has no filesystem support. However,
this escape route can be integrated directly into the select_file
method. This will give us the benefit that it will work transparently
in all code locations.
(This also means we can get rid of the select_parent method again)
Related: OS#6120
Change-Id: Ie6f37d13af880d24a9c7a8a95cef436b603587c7
8597b64ee6