Thumb drive contents aren't refreshed automatically in some cases

## What Happened
I've been sneaker-netting files from my Mac to my Elementary OS box using a thumb drive. What I noticed is, on occasion, Files is showing me cached contents of the thumb drive after the drive was mounted and re-mounted. I have to manually refresh the drive listing using ctrl-r to get the new contents listed. I can't figure out when exactly this happens and when it doesn't, but I thought I should get it in the tracker.

## Expected Behavior

When the drive is mounted, the current contents of the drive to be listed in Files, not a cached listing.

## Steps to Reproduce

1. Put file "A" on a thumb drive from machine 1
2. Mount thumb drive on EOS, machine 2, select it in the Files sidebar
3. Eject thumb drive on EOS, don't close the Files window
4. Put thumb drive in machine 1, delete file "A"
5. Copy a new file onto the thumb drive, file "B"
6. Mount thumb drive on EOS, machine 2, select it in the Files sidebar
7. Note thumb drive contents _may_ still show the old file listing until refreshed.

### Logs

I'd be happy to provide any requested logs

## Platform Information
* Elementary OS 5.1.7, fully up to date
* Thumb drive is msdos formatted