use the ZT_SET_DIALPARAMS ioctl properly by initializing the structure to all zeroes in case it contains fields that we don't write values into (which it does as of Zaptel 1.4.10)

(closes issue #12456)
Reported by: fnordian



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@114184 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_zap.c

@@ -11216,6 +11216,8 @@ static int process_zap(struct zt_chan_conf *confp, struct ast_variable *v, int r
 
 				toneduration = atoi(v->value);
 				if (toneduration > -1) {
+					memset(&dps, 0, sizeof(dps));
+
 					dps.dtmf_tonelen = dps.mfv1_tonelen = toneduration;
 					res = ioctl(ctlfd, ZT_SET_DIALPARAMS, &dps);
 					if (res < 0) {