Update 260_crypt_layout.sh

If more than one keyslot is used in LUKS header the 'grep' command
looking for 'Cipher key' would return more than one line.
But we need just one value. Use 'key_size' from the first found key.

usr/share/rear/layout/save/GNU/Linux/260_crypt_layout.sh

@@ -74,7 +74,8 @@ while read target_name junk ; do
         hash=$( grep "Hash spec" $TMP_DIR/cryptsetup.luksDump | sed -r 's/^.+:\s*(.+)$/\1/' )
     elif test $luks_type = "luks2" ; then
         cipher=$( grep "cipher:" $TMP_DIR/cryptsetup.luksDump | sed -r 's/^.+:\s*(.+)$/\1/' )
-        key_size=$( grep "Cipher key" $TMP_DIR/cryptsetup.luksDump | sed -r 's/^.+:\s*(.+) bits$/\1/' )
+        # More than one keyslot may be defined - use key_size from the first slot
+        key_size=$( grep -m 1 "Cipher key" $TMP_DIR/cryptsetup.luksDump | sed -r 's/^.+:\s*(.+) bits$/\1/' )
         hash=$( grep "Hash" $TMP_DIR/cryptsetup.luksDump | sed -r 's/^.+:\s*(.+)$/\1/' )
     fi