[IOT-1413,IOT-1415] Fixed request handling bugs for /oic/ping resource

[IOT-1413,IOT-1415] Fixed request handling bugs for /oic/ping resource

- /oic/ping resource is responding with 5.00(internal server error)
when it receives a GET/POST/PUT request with baseline query
- /oic/ping resource is successfully registering and deregistering
observe requests, even though it is shown as non observable resource
in discovery response.

Change-Id: I86db52f17b0b42750906fdfa8b377c78a85ef822
Signed-off-by: hyuna0213.jo <hyuna0213.jo@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13089
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jaehong Jo <jaehong.jo@samsung.com>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>