FT-273 Fixup a bug and a few tests

ft/ft.cc

@@ -387,7 +387,8 @@ static void ft_init(FT ft, FT_OPTIONS options, CACHEFILE cf) {
 
     toku_list_init(&ft->live_ft_handles);
 
-    ft->cmp.create(options->compare_fun, &ft->descriptor);
+    // intuitively, the comparator points to the FT's cmp descriptor
+    ft->cmp.create(options->compare_fun, &ft->cmp_descriptor);
     ft->update_fun = options->update_fun;
 
     if (ft->cf != NULL) {

ft/tests/ft-serialize-benchmark.cc

@@ -420,7 +420,6 @@ test_serialize_nonleaf(int valsize, int nelts, double entropy, int ser_runs, int
     toku_free(ft);
     toku_free(ndd);
     toku_free(ndd2);
-    cmp.destroy();
 
     r = close(fd); assert(r != -1);
 }

ft/tests/ft-serialize-test.cc

@@ -1125,12 +1125,12 @@ test_serialize_nonleaf(enum ftnode_verify_type bft, bool do_clone) {
 
     toku_block_free(ft_h->blocktable, BLOCK_ALLOCATOR_TOTAL_HEADER_RESERVE);
     toku_blocktable_destroy(&ft_h->blocktable);
+    ft_h->cmp.destroy();
     toku_free(ft_h->h);
     toku_free(ft_h);
     toku_free(ft);
     toku_free(src_ndd);
     toku_free(dest_ndd);
-    cmp.destroy();
 
     r = close(fd); assert(r != -1);
 }