[#92] Embed policer's objectsInWork mutex

Signed-off-by: Alejandro Lopez <a.lopez@yadro.com>

pkg/services/policer/policer.go

@@ -11,28 +11,28 @@ import (
 )
 
 type objectsInWork struct {
-	m    sync.RWMutex
+	sync.RWMutex
 	objs map[oid.Address]struct{}
 }
 
 func (oiw *objectsInWork) inWork(addr oid.Address) bool {
-	oiw.m.RLock()
+	oiw.RLock()
 	_, ok := oiw.objs[addr]
-	oiw.m.RUnlock()
+	oiw.RUnlock()
 
 	return ok
 }
 
 func (oiw *objectsInWork) remove(addr oid.Address) {
-	oiw.m.Lock()
+	oiw.Lock()
 	delete(oiw.objs, addr)
-	oiw.m.Unlock()
+	oiw.Unlock()
 }
 
 func (oiw *objectsInWork) add(addr oid.Address) {
-	oiw.m.Lock()
+	oiw.Lock()
 	oiw.objs[addr] = struct{}{}
-	oiw.m.Unlock()
+	oiw.Unlock()
 }
 
 // Policer represents the utility that verifies