cgen: dump the codegen after it has been updated

On bf_cgen_update(), the codegen is dumped (if verbose is enabled) very
early in the function, meaning the old (to be replaced) chain is
printed.

Dump the codegen at the end of the function, when the chain replacement
occurred, so the new chain is printed.

src/bpfilter/cgen/cgen.c

@@ -242,9 +242,6 @@ int bf_cgen_update(struct bf_cgen *cgen, struct bf_chain **new_chain)
 
     bf_assert(cgen && new_chain);
 
-    if (bf_opts_is_verbose(BF_VERBOSE_DEBUG))
-        bf_cgen_dump(cgen, EMPTY_PREFIX);
-
     r = bf_program_new(&new_prog, (*new_chain)->hook, cgen->front, *new_chain);
     if (r < 0)
         return bf_err_r(r, "failed to create a new bf_program");
@@ -264,5 +261,8 @@ int bf_cgen_update(struct bf_cgen *cgen, struct bf_chain **new_chain)
     bf_swap(cgen->program, new_prog);
     bf_swap(cgen->chain, *new_chain);
 
+    if (bf_opts_is_verbose(BF_VERBOSE_DEBUG))
+        bf_cgen_dump(cgen, EMPTY_PREFIX);
+
     return 0;
 }