manager: Fix tests hanging (fixes #2)

I'm not 100% sure why this works, but I expect it has to do with messages being sent to D-Bus before the initial handshake is done.

src/manager/root.rs

@@ -323,7 +323,9 @@ mod test {
     use crate::power::{self, get_gpu_performance_level};
     use crate::process::test::{code, exit, ok};
     use crate::testing;
+    use std::time::Duration;
     use tokio::fs::{create_dir_all, write};
+    use tokio::time::sleep;
     use zbus::{Connection, ConnectionBuilder};
 
     struct TestHandle {
@@ -351,6 +353,8 @@ mod test {
             .at("/com/steampowered/SteamOSManager1", manager)
             .await?;
 
+        sleep(Duration::from_millis(1)).await;
+
         Ok(TestHandle {
             h: handle,
             connection,

src/manager/user.rs

@@ -365,7 +365,9 @@ mod test {
 
     use std::collections::{HashMap, HashSet};
     use std::iter::zip;
+    use std::time::Duration;
     use tokio::fs::read;
+    use tokio::time::sleep;
     use zbus::{Connection, ConnectionBuilder, Interface};
     use zbus_xml::{Method, Node, Property};
 
@@ -384,6 +386,8 @@ mod test {
             .at("/com/steampowered/SteamOSManager1", manager)
             .await?;
 
+        sleep(Duration::from_millis(1)).await;
+
         Ok(TestHandle {
             _handle: handle,
             connection,