Fixed failed tests of RE cache module.

Fixed failed tests of RE cache module.

The cause was calling a method not mocked.

Change-Id: I74e20d34d793085e9888f634bb1a5e060f09e0ee
Signed-off-by: coderhyme <jhyo.kim@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/7709
Reviewed-by: JungYong KIM <jyong2.kim@samsung.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
(cherry picked from commit 4fa510cdc72a7412fcae654d031b7d3bff9b1800)
Reviewed-on: https://gerrit.iotivity.org/gerrit/7725