Revert series: virtiofsd: Announce submounts to the guest

This reverts the following commits due to their basis on a bogus
linux kernel header update:

c93a656f ("tests/acceptance: Add virtiofs_submounts.py")
45ced7ca ("tests/acceptance/boot_linux: Accept SSH pubkey")
08dce386 ("virtiofsd: Announce sub-mount points")
eba8b096 ("virtiofsd: Store every lo_inode's parent_dev")
ede24b6b ("virtiofsd: Add fuse_reply_attr_with_flags()")
e2577435 ("virtiofsd: Add attr_flags to fuse_entry_param")
2f10415a ("virtiofsd: Announce FUSE_ATTR_FLAGS")
97d741cc ("linux/fuse.h: Pull in from Linux")

Cc: Max Reitz <mreitz@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 160385090886.20017.13382256442750027666.stgit@gimli.home
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>