network: Fix request ecdhCurve mismatch errors.

The HTTP Node now uses auto for ecdhCurve for SSL connections. This fixes the SSL
handshake error while connecting to some Zulip instances. Setting the ecdhCurve to auto
is the recommended method for Node > 8.5, more info here -
nodejs/node#16196

Fixes: zulip#594.

app/main/linuxupdater.js

@@ -21,7 +21,8 @@ function linuxUpdateNotification() {
 	const options = {
 		url,
 		headers: {'User-Agent': 'request'},
-		proxy: proxyEnabled ? ProxyUtil.getProxy(url) : ''
+		proxy: proxyEnabled ? ProxyUtil.getProxy(url) : '',
+		ecdhCurve: 'auto'
 	};
 
 	request(options, (error, response, body) => {

app/renderer/js/utils/domain-util.js

@@ -129,7 +129,8 @@ class DomainUtil {
 		const checkDomain = {
 			url: domain + '/static/audio/zulip.ogg',
 			ca: (certificateLocation) ? certificateLocation : '',
-			proxy: proxyEnabled ? ProxyUtil.getProxy(domain) : ''
+			proxy: proxyEnabled ? ProxyUtil.getProxy(domain) : '',
+			ecdhCurve: 'auto'
 		};
 
 		const serverConf = {
@@ -206,7 +207,8 @@ class DomainUtil {
 		const proxyEnabled = ConfigUtil.getConfigItem('useManualProxy') || ConfigUtil.getConfigItem('useSystemProxy');
 		const serverSettingsOptions = {
 			url: domain + '/api/v1/server_settings',
-			proxy: proxyEnabled ? ProxyUtil.getProxy(domain) : ''
+			proxy: proxyEnabled ? ProxyUtil.getProxy(domain) : '',
+			ecdhCurve: 'auto'
 		};
 		return new Promise((resolve, reject) => {
 			request(serverSettingsOptions, (error, response) => {
@@ -232,7 +234,8 @@ class DomainUtil {
 		const proxyEnabled = ConfigUtil.getConfigItem('useManualProxy') || ConfigUtil.getConfigItem('useSystemProxy');
 		const serverIconOptions = {
 			url,
-			proxy: proxyEnabled ? ProxyUtil.getProxy(url) : ''
+			proxy: proxyEnabled ? ProxyUtil.getProxy(url) : '',
+			ecdhCurve: 'auto'
 		};
 		// The save will always succeed. If url is invalid, downgrade to default icon.
 		return new Promise(resolve => {