Changed client keepalive logic to use the dynamic interval value

Changed client keepalive logic to use the dynamic interval value

According to the OIC Spec, keepalive interval of D2D start from
2 minutes and increases in multiples of 2 up to a maximum of 64
minutes. but the interval value for D2S can be defined by the
cloud server. so if response message includes the interval array
property, Device use the interval value received from remote device.

Change-Id: I6dea8a082f1c221667c61985f28678bf310e66f2
Signed-off-by: hyuna0213.jo <hyuna0213.jo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/4719
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jon A. Cruz <jonc@osg.samsung.com>