res_rtp_asterisk: Don't leak memory or reset state if DTLS configuration is set multiple times.

........

Merged revisions 417705 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@417706 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_rtp_asterisk.c

@@ -902,6 +902,10 @@ static int ast_rtp_dtls_set_configuration(struct ast_rtp_instance *instance, con
 		return -1;
 	}
 
+	if (rtp->ssl_ctx) {
+		return 0;
+	}
+
 	if (!(rtp->ssl_ctx = SSL_CTX_new(DTLSv1_method()))) {
 		return -1;
 	}