Correct observe callback function in occlient.

Correct observe callback function in occlient.

1. For observe register request, Sequence number received
in client response falls in range 0 - MAX_SEQUENCE_NUMBER.
2. For observe deregister request and or any failed requests,
the client sequence number value is MAX_SEQUENCE_NUMBER + 1.

Change-Id: Idcc0775179e17ce6df85fb93f127336fede9a42a
Signed-off-by: Ziran Sun <ziran.sun@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/11695
Reviewed-by: Habib Virji <habib.virji@samsung.com>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>