Don't download E2E devices if feature disabled

If the user hasn't enabled the E2E setting in the labs, there is no point in
firing off the device download request when the MemberInfo is opened.

src/components/views/rooms/MemberInfo.js

@@ -73,6 +73,11 @@ module.exports = React.createClass({
     },
 
     componentDidMount: function() {
+        // only display the devices list if our client supports E2E *and* the
+        // feature is enabled in the user settings
+        this._enableDevices = MatrixClientPeg.get().isCryptoEnabled() &&
+            UserSettingsStore.isFeatureEnabled("e2e_encryption");
+
         this._updateStateForNewMember(this.props.member);
         MatrixClientPeg.get().on("deviceVerificationChanged", this.onDeviceVerificationChanged);
     },
@@ -147,6 +152,10 @@ module.exports = React.createClass({
     },
 
     onDeviceVerificationChanged: function(userId, device) {
+        if (!this._enableDevices) {
+            return;
+        }
+
         if (userId == this.props.member.userId) {
             // no need to re-download the whole thing; just update our copy of
             // the list.
@@ -170,6 +179,10 @@ module.exports = React.createClass({
     },
 
     _downloadDeviceList: function(member) {
+        if (!this._enableDevices) {
+            return;
+        }
+
         var cancelled = false;
         this._cancelDeviceList = function() { cancelled = true; }
 
@@ -532,7 +545,7 @@ module.exports = React.createClass({
     },
 
     _renderDevices: function() {
-        if (!UserSettingsStore.isFeatureEnabled("e2e_encryption")) {
+        if (!this._enableDevices) {
             return null;
         }