Clear existing extension state.

When parsing ClientHello clear any existing extension state from
SRP login and SRTP profile.

Thanks to Karthikeyan Bhargavan for reporting this issue.
Reviewed-by: Matt Caswell <matt@openssl.org>

(cherry picked from commit 4f605ccb77)

Conflicts:
	ssl/t1_lib.c

ssl/t1_lib.c

@@ -2016,6 +2016,16 @@ static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p, unsigned char
 		s->cert->peer_sigalgs = NULL;
 		}
 
+#ifndef OPENSSL_NO_SRP
+	if (s->srp_ctx.login != NULL)
+		{
+		OPENSSL_free(s->srp_ctx.login);
+		s->srp_ctx.login = NULL;
+		}
+#endif
+
+	s->srtp_profile = NULL;
+
 	if (data >= (d+n-2))
 		goto ri_check;
 	n2s(data,len);