libblkid: trust in udev symlinks, don't verify

libblkid: trust in udev symlinks, don't verify

The libblkid always verify that /dev/disk/by-* symlinks match with
on-device LABELs/UUIDs. It means that all requests (e.g. mount -L |
-U) generates extra superblocks scans on the device.

Currently, many users and tools (GNOME, systemd, ...etc) use the
symlink directly and udev maintains the symlinks by inotify (+watch
rule). It seems better for system performance to disable the extra
paranoid mode and trust in udev.

Signed-off-by: Karel Zak <kzak@redhat.com>