ssl_create_cipher_list: check whether push onto cipherstack succeeds

(Imported from upstream's f5905ba341ad0fa3731469f10f7fba6f92ecd787.)

Change-Id: I92f2f53a127a4f59ce71cf00a9a4aedd0560e586
Reviewed-on: https://boringssl-review.googlesource.com/2832
Reviewed-by: Adam Langley <agl@google.com>