apparmor: aa_label_alloc use aa_label_free on alloc failure

In the Linux kernel, the following vulnerability has been resolved: apparmor: aa_label_alloc use aa_label_free on alloc failure aa_label_alloc() allocates a secid before allocating or taking the label proxy. If the later proxy step fails, the error path only freed the label memory, leaking any resources initialized by aa_label_init(). Use aa_label_free() on the failure path so partially initialized labels release their secid and other label resources before the backing memory is freed.