btrfs-progs: fsck-tests: Move reloc tree images to 020-extent-ref-cases

For reloc tree, despite of its short lifespan, it's still the backref,
where reloc tree root backref points back to itself, makes it special.

So it's more approriate to put them into 020-extent-ref-cases.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

tests/fsck-tests/015-tree-reloc-tree/test.sh

@@ -1,16 +0,0 @@
-#!/bin/bash
-# Make sure btrfs check won't report any false alerts for valid image with
-# reloc tree.
-#
-# Also due to the short life span of reloc tree, save the as dump example for
-# later usage.
-
-source "$TEST_TOP/common"
-
-check_prereq btrfs
-
-check_image() {
-	run_check "$TOP/btrfs" check "$1"
-}
-
-check_all_images

tests/fsck-tests/020-extent-ref-cases/test.sh

@@ -14,6 +14,11 @@
 #   Containing a block group and its first extent at
 #   the beginning of leaf.
 #   Which caused false alert for lowmem mode.
+#
+# Special cases with some rare backref types
+# * reloc tree
+#   For both fs tree and data reloc tree.
+#   Special for its backref pointing to itself and its short life span.
 
 source "$TEST_TOP/common"