to add error checker for gatt connection state

to add error checker for gatt connection state

- it handles to process retry as per states for gatt connection state.
- to add code which waiting for target device for unicast.

Change-Id: Idc558154895792027a9535bb61558d483fb04148
Signed-off-by: jihwan.seo <jihwan.seo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/5193
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jon A. Cruz <jonc@osg.samsung.com>