VOL-2293, VOL-2456 improve error handling

Change-Id: I4be5f12719a31b40363758cd47cc02968f180c75
diff --git a/adaptercore/olt_state_transitions_test.go b/adaptercore/olt_state_transitions_test.go
index 6c256a1..c79aeb0 100644
--- a/adaptercore/olt_state_transitions_test.go
+++ b/adaptercore/olt_state_transitions_test.go
@@ -18,7 +18,6 @@
 
 import (
 	"context"
-	"errors"
 	"reflect"
 	"testing"
 	"time"
@@ -48,7 +47,7 @@
 		after: []TransitionHandler{func(ctx context.Context) error {
 			return nil
 		}, func(ctx context.Context) error {
-			return errors.New("transition error")
+			return ErrStateTransition
 		}},
 	}
 	transitions[GrpcConnected] = transition
@@ -66,7 +65,7 @@
 		before: []TransitionHandler{func(ctx context.Context) error {
 			return nil
 		}, func(ctx context.Context) error {
-			return errors.New("transition error")
+			return ErrStateTransition
 		}},
 	}
 	transitions[GrpcConnected] = transition