Restore handshake_cutthrough accidentally disabled by renegotiation support

This fixes a problem introduced in 4a25f3f3e49e952616d0d47167c157904908c156

Tracking CL 17037347

Oops: we disabled False Start even for initial handshakes by checking
previous_client_finished_len (which will be > 0 since this is after
ssl3_send_finished()) instead of previous_server_finished_len (== 0
before first ssl3_get_finished(), i.e. in the initial handshake when
we'd want to do a False Start).

Change-Id: Id919c4e912be3bed9a0bd5755ebbf82de2d4784e
diff --git a/ssl/ssl_lib.c b/ssl/ssl_lib.c
index 94e5e8d..e120dad 100644
--- a/ssl/ssl_lib.c
+++ b/ssl/ssl_lib.c
@@ -3066,7 +3066,7 @@
 		s->s3->in_read_app_data == 0 &&   /* cutthrough only applies to write() */
 		(SSL_get_mode((SSL*)s) & SSL_MODE_HANDSHAKE_CUTTHROUGH) &&  /* cutthrough enabled */
 		SSL_get_cipher_bits(s, NULL) >= 128 &&                      /* strong cipher choosen */
-		s->s3->previous_client_finished_len == 0 &&                 /* not a renegotiation handshake */
+		s->s3->previous_server_finished_len == 0 &&                 /* not a renegotiation handshake */
 		(s->state == SSL3_ST_CR_SESSION_TICKET_A ||                 /* ready to write app-data*/
 			s->state == SSL3_ST_CR_FINISHED_A));
 	}