Fix netplan configuration on Debian 12.

Drop in netplan files with higher priority rather than deleting the defaults.

google_guest_agent/network/manager/netplan_linux.go

@@ -145,6 +145,11 @@ func (n netplan) Name() string {
 // Configure gives the opportunity for the Service implementation to adjust its configuration
 // based on the Guest Agent configuration.
 func (n netplan) Configure(ctx context.Context, config *cfg.Sections) {
+	osInfo := osinfoGet()
+	// Debian's default netplan configuration is priority 90.
+	if osInfo.OS == "debian" && osInfo.Version.Major == 12 {
+		n.priority = 91
+	}
 }
 
 // IsManaging checks whether netplan is present in the system.
@@ -181,15 +186,6 @@ func (n netplan) SetupEthernetInterface(ctx context.Context, config *cfg.Section
 		return fmt.Errorf("error writing systemd-networkd's drop-in: %v", err)
 	}
 
-	osInfo := osinfoGet()
-	// Debian 12 has a pretty generic matching netplan configuration for gce, until we have that
-	// changed we are only removing.
-	if osInfo.OS == "debian" && osInfo.Version.Major == 12 {
-		if err := os.Remove("/etc/netplan/90-default.yaml"); err != nil {
-			logger.Debugf("Failed to remove default netplan config: %s", err)
-		}
-	}
-
 	// Avoid restarting systemd-networkd.
 	if err := run.Quiet(ctx, "networkctl", "reload"); err != nil {
 		return fmt.Errorf("error reloading systemd-networkd network configs: %v", err)