Increase max timeout for client reboot

1 minute may not be enough, as per
https://github.com/ubuntu/adsys/actions/runs/8195833180/job/22414854516

e2e/internal/remote/remote.go

@@ -231,7 +231,7 @@ func (c Client) Upload(localPath string, remotePath string) error {
 // Reboot reboots the remote host and waits for it to come back online, then
 // reestablishes the SSH connection.
 // It first waits for the host to go offline, then returns an error if the host
-// does not come back online within 1 minute.
+// does not come back online within 3 minutes.
 func (c *Client) Reboot() error {
 	log.Infof("Rebooting host %q", c.client.RemoteAddr().String())
 	_, _ = c.Run(context.Background(), "reboot")
@@ -251,7 +251,7 @@ func (c *Client) Reboot() error {
 		return fmt.Errorf("host did not go offline in time")
 	}
 
-	ctx, cancel := context.WithTimeout(context.Background(), time.Minute)
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Minute)
 	defer cancel()
 
 	// Wait for the host to come back online