Switching to last workspace only works when last switch is done by vswitch

[lilydjwg]

Describe the bug

#1371 doesn't fully implement #1296.

To Reproduce Steps to reproduce the behavior:

1. Enable plugin vswitch and expo
2. Switch workspace with expo
3. Try switch back with vswitch
4. vswitch tries to reverse its last action instead, which fails or is wrong because the last switch is done by other plugins

Expected behavior Workspace should be switched back.

Screenshots or stacktrace

Wayfire version git