[client] Fix state manager race conditions (#2890)

client/internal/routemanager/systemops/state.go

@@ -2,31 +2,28 @@ package systemops
 
 import (
 	"net/netip"
-	"sync"
 
 	"github.com/netbirdio/netbird/client/internal/routemanager/refcounter"
 )
 
-type ShutdownState struct {
-	Counter *ExclusionCounter `json:"counter,omitempty"`
-	mu      sync.RWMutex
-}
+type ShutdownState ExclusionCounter
 
 func (s *ShutdownState) Name() string {
 	return "route_state"
 }
 
 func (s *ShutdownState) Cleanup() error {
-	s.mu.RLock()
-	defer s.mu.RUnlock()
-
-	if s.Counter == nil {
-		return nil
-	}
-
 	sysops := NewSysOps(nil, nil)
 	sysops.refCounter = refcounter.New[netip.Prefix, struct{}, Nexthop](nil, sysops.removeFromRouteTable)
-	sysops.refCounter.LoadData(s.Counter)
+	sysops.refCounter.LoadData((*ExclusionCounter)(s))
 
 	return sysops.refCounter.Flush()
 }
+
+func (s *ShutdownState) MarshalJSON() ([]byte, error) {
+	return (*ExclusionCounter)(s).MarshalJSON()
+}
+
+func (s *ShutdownState) UnmarshalJSON(data []byte) error {
+	return (*ExclusionCounter)(s).UnmarshalJSON(data)
+}