xl: don't leak a lot of memory in forked process in domain_create

A goto statement skips over freeing data structures for no good reason.
It's not a real issue since the next step is to exit() but this cleans
up output of valgrind so that other leaks and errors can be spotted.

Signed-off-by: Gianni Tedesco <gianni.tedesco@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>

tools/libxl/xl_cmdimpl.c

@@ -1511,7 +1511,7 @@ start:
                 goto error_out;
             }
             ret = domid;
-            goto waitpid_out;
+            goto out;
         }
 
         rc = libxl_ctx_postfork(&ctx);