WireGuard peers can be configured by their DNS name, which NetworkManager will resolve.
Since activating a profile might affect now names get resolved, we must first resolve names before completing the activation of the WireGuard device (and before reconfiguring DNS accordingly).
For example, if you configure exclusive DNS resolution via the WireGuard device, and if the peer needs to be resolved via DNS, then resolving the peer name must block the reconfiguration of DNS.
Fix that by waiting.