Clear connection options and status fields in free_connection_partially().

Most fields should be zero when reusing a connection. In particular, when an
outgoing connection to a node which is reachable on more than one address is
made, the second connection to that node will have status.encryptout set but
outctx will be NULL, causing a NULL pointer dereference when
EVP_EncryptUpdate() is called in send_meta() when it shouldn't.