Addresses #679 refs[t:679] On upgrade from layout_version 10->11, remove checkpoint lsn from header

git-svn-id: file:///svn/toku/tokudb@14480 c7de825b-a66e-492c-adef-691d508d4ae1

newbrt/backwards_10.c

@@ -400,6 +400,7 @@ upgrade_brtheader_10_11(struct brt_header **brth_10, struct brt_header ** brth_1
     *brth_10 = NULL;
     (*brth_11)->layout_version = BRT_LAYOUT_VERSION_11;
     (*brth_11)->layout_version_original = BRT_LAYOUT_VERSION_10;
+    (*brth_11)->checkpoint_lsn = ZERO_LSN; //Can't reuse LSNs
     return 0;
 }