fixed Resource-encapsulation sampleApplication bug.

fixed Resource-encapsulation sampleApplication bug.

- when called 'getCachedAttribute' function, client can't get cached attribute because of mismatching key of 'attribute'.

Change-Id: I6248d2ff34d422fae4b8daf4df8b50804f4745b7
Signed-off-by: Heewon Park <h_w.park@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/3803
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
(cherry picked from commit 3bc14f90ecafe7a5ebfae2f25015d5be11e38ff9)
Reviewed-on: https://gerrit.iotivity.org/gerrit/3809