These aren't perfect, but the tool is pretty much hostile to proper
completions - it includes a "--machine-readable" option, but `vagrant
global-status --machine-readable` prints great output like
```
1551816037,,ui,info,id
1551816037,,ui,info,name
1551816037,,ui,info,provider
1551816037,,ui,info,state
1551816037,,ui,info,directory
1551816037,,ui,info,
1551816037,,ui,info,-------------------------------------------------------------------------
1551816037,,ui,info,d3ea265
1551816037,,ui,info,default
1551816037,,ui,info,virtualbox
1551816037,,ui,info,poweroff
1551816037,,ui,info,/home/alfa/dev/oi-userland
1551816037,,ui,info,
1551816037,,ui,info,fdf42c4
1551816037,,ui,info,default
1551816037,,ui,info,virtualbox
1551816037,,ui,info,poweroff
1551816037,,ui,info,/home/alfa/dev/vagrant/NetBSD
1551816037,,ui,info,
1551816037,,ui,info,f8f6eff
1551816037,,ui,info,default
1551816037,,ui,info,virtualbox
1551816037,,ui,info,poweroff
1551816037,,ui,info,/home/alfa/dev/vagrant/fedora
1551816037,,ui,info,
1551816037,,ui,info, \nThe above shows information about all known Vagrant environments\non this machine. This data is cached and may not be completely\nup-to-date (use "vagrant global-status --prune" to prune invalid\nentries). To interact with any of the machines%!(VAGRANT_COMMA) you can go to that\ndirectory and run Vagrant%!(VAGRANT_COMMA) or you can use the ID directly with\nVagrant commands from any directory. For example:\n"vagrant destroy 1a2b3c4d"
```
and still takes 500ms to do so. The actual information is in a json
file, which we can't expect to read, and it doesn't have linebreaks or
such which we could use to hack-parse it.
So this is the best we can do for the most important bits (the
machineids), so let's just add this as-is.
[ci skip]
