Incr Ext4: Properly merge block_allocation lists

BUG: 27698960
Change-Id: Ia31b8319e0d1c8644ae1798116007a4b35c39e9b
Signed-off-by: Mohamad Ayyash <mkayyash@google.com>
diff --git a/ext4_utils/extent.c b/ext4_utils/extent.c
index 42ddd97..7887488 100644
--- a/ext4_utils/extent.c
+++ b/ext4_utils/extent.c
@@ -96,7 +96,7 @@
 						block_len + 1 - prealloc_block_len);
 				return NULL;
 			}
-			region_list_append(&prealloc->list, alloc->list.first);
+			region_list_merge(&prealloc->list, &alloc->list);
 			free(alloc);
 		}
 		alloc = prealloc;