libblkid: open device in nonblock mode.

libblkid: open device in nonblock mode.

When autoclose is set (kernel default but many distributions reverse the
setting) opening a CD-rom device causes the tray to close.

The function of blkid is to report the current state of the device and
not to change it. Hence it should use O_NONBLOCK when opening the
device to avoid closing a CD-rom tray.

blkid is used liberally in scripts so it can potentially interfere with
the user operating the CD-rom hardware.

[kzak@redhat.com: add O_NONBLOCK also to:
                  - wipefs
                  - blkid_new_probe_from_filename()
                  - blkid_evaluate_tag()]

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
Signed-off-by: Karel Zak <kzak@redhat.com>