Removing media folder should stop media library scan.

[bpcomp13]

Problem description

When attempting to add a media folder, if you add a top level folder suck as / there does not appear to be any way to stop a media folder scan. Deleting the media folder should stop media scanning of that folder.

Steps to reproduce

1. Add a media folder with folder location of /
2. Click the scan media folders now

System information

• Airsonic version: 2009.1.0 – September 15, 2020, based on Airsonic 8b28366 from Docker
• Operating system: Ubuntu 16.04 LTS
• Java version: java 1.8.0_265
• Proxy server: None
• Client: Chrome 85.0.4183.102 and Firefox 80.0.1
• Language: English

[popeen]

Yeah, having a way to stop the scan sounds like a really good idea