PLT-3332 Removed multiple change channel header messages (#3390)

* disabled submit upon form submission to avoid asynchronous errors

* Used state instead of props

webapp/components/edit_channel_header_modal.jsx

@@ -36,7 +36,8 @@ class EditChannelHeaderModal extends React.Component {
 
         this.state = {
             header: props.channel.header,
-            serverError: ''
+            serverError: '',
+            submitted: false
         };
     }
 
@@ -55,7 +56,8 @@ class EditChannelHeaderModal extends React.Component {
     componentWillReceiveProps(nextProps) {
         if (this.props !== nextProps) {
             this.setState({
-                header: nextProps.channel.header
+                header: nextProps.channel.header,
+                submitted: false
             });
         }
     }
@@ -77,6 +79,8 @@ class EditChannelHeaderModal extends React.Component {
     }
 
     handleSubmit() {
+        this.setState({submitted: true});
+
         Client.updateChannelHeader(
             this.props.channel.id,
             this.state.header,
@@ -102,6 +106,7 @@ class EditChannelHeaderModal extends React.Component {
     onShow() {
         const textarea = ReactDOM.findDOMNode(this.refs.textarea);
         Utils.placeCaretAtEnd(textarea);
+        this.submitted = false;
     }
 
     onHide() {
@@ -190,6 +195,7 @@ class EditChannelHeaderModal extends React.Component {
                         />
                     </button>
                     <button
+                        disabled={this.state.submitted}
                         type='button'
                         className='btn btn-primary'
                         onClick={this.handleSubmit}

webapp/components/edit_channel_purpose_modal.jsx

@@ -31,7 +31,8 @@ export default class EditChannelPurposeModal extends React.Component {
         this.ctrlSend = PreferenceStore.getBool(Constants.Preferences.CATEGORY_ADVANCED_SETTINGS, 'send_on_ctrl_enter');
 
         this.state = {
-            serverError: ''
+            serverError: '',
+            submitted: false
         };
     }
 
@@ -75,6 +76,9 @@ export default class EditChannelPurposeModal extends React.Component {
         if (!this.props.channel) {
             return;
         }
+
+        this.setState({submitted: true});
+
         Client.updateChannelPurpose(
             this.props.channel.id,
             ReactDOM.findDOMNode(this.refs.purpose).value.trim(),
@@ -189,6 +193,7 @@ export default class EditChannelPurposeModal extends React.Component {
                     <button
                         type='button'
                         className='btn btn-primary'
+                        disabled={this.state.submitted}
                         onClick={this.handleSave}
                     >
                         <FormattedMessage