Set editing to false on request error

Closes PLAT-4574

Test Plan:
Create an LTI key via pasting JSON. Use invalid JSON on first
attempt. Verify you can then use valid JSON without refreshing.

Change-Id: Ic0be5675951649aeafda3002d47f4aac786354b5
Reviewed-on: https://gerrit.instructure.com/196889
Reviewed-by: Drake Harper <dharper@instructure.com>
Reviewed-by: Marc Phillips <mphillips@instructure.com>
Reviewed-by: Kai Bjorkman <kbjorkman@instructure.com>
QA-Review: Marc Phillips <mphillips@instructure.com>
Tested-by: Jenkins
Product-Review: Weston Dransfield <wdransfield@instructure.com>

app/jsx/developer_keys/actions/ltiKeyActions.js

@@ -124,6 +124,7 @@ actions.saveLtiToolConfiguration = ({
     })
     .catch(error => {
       dispatch(actions.saveLtiToolConfigurationFailed(error))
+      dispatch(developerKeysActions.setEditingDeveloperKey(false))
       $.flashError(error.message)
       return error
     })