Fix memory leak in SSL_new if errors occur.

(Imported from upstream's 76e6509085ea96df0ca542568ee2596343711307)

Change-Id: I6319271a1f46b3d36a4eba950cbab60420126175
Reviewed-on: https://boringssl-review.googlesource.com/2833
Reviewed-by: Adam Langley <agl@google.com>