fuse: Reopen file and skip to desired offset if seek is not supported
The fuse daemon can fail when client attempts to seek backwards and seek
is not supported by the concrete backend. There is fallback for forward
g_input_stream_skip. Let's reopen the file and use the same
approach also for backwards seeks. This is pretty ugly to reopen the file
but similar approach is used already to emulate read/write mode.
Fixes: #441 (closed)