Fix an inaccurate log when validating allowDowngrade parameter during Agent update

cr: https://code.amazon.com/reviews/CR-123693017

Author: HaoranREN

agent/update/processor/processor.go

@@ -354,7 +354,7 @@ func validateUpdateParam(mgr *updateManager, logger log.T, updateDetail *UpdateD
 
 		if !updateDetail.AllowDowngrade {
 			logger.Warnf("Downgrade is not enabled, please enable downgrade to perform this update")
-			return mgr.failed(updateDetail, logger, updateconstants.ErrorAttemptToDowngrade, fmt.Sprintf("Updating %v to an older version, please enable allow downgrade to proceed", updateDetail.TargetVersion), true)
+			return mgr.failed(updateDetail, logger, updateconstants.ErrorAttemptToDowngrade, fmt.Sprintf("Updating %v to an older version %v, please enable allow downgrade to proceed", updateDetail.SourceVersion, updateDetail.TargetVersion), true)
 		}
 	}
 

agent/update/processor/processor_test.go

@@ -939,7 +939,7 @@ func TestValidateUpdateParam_FailedAttemptDowngrade_AllowDowngradeFalse(t *testi
 	assert.Equal(t, contracts.ResultStatusFailed, updateDetail.Result)
 	assert.True(t, updateDetail.RequiresUninstall)
 
-	assert.Contains(t, updateDetail.StandardOut, "to an older version, please enable allow downgrade to proceed")
+	assert.Contains(t, updateDetail.StandardOut, "Updating 3.0.0.0 to an older version 2.0.0.0, please enable allow downgrade to proceed")
 	assert.Equal(t, "", updateDetail.StandardError)
 }