Error message with a custom image URL doesn't clear

[webteam-app]

Bug originally filed by d0ugal at https://bugs.launchpad.net/bugs/1890262

When using a new MAAS install and you are selecting the images. If you select a custom image and add a invalid URL (i.e. you forget the / at the end) you will get a error like;

Error:Failed to parse: 10.177.244.6:8000streams

After correcting this the error isn't cleared. Incidently we could probably add the trailing slash if it missing.

[Caleb-Ellis]

This was fixed in the React migration of the Images page