Fix deleting request on slow response

Fix deleting request on slow response

Server request is getting deleted when observe request
received again with same previous request token even
the new server request is not being added to sever request
list. Duplicate requests with same token are expected when
when ACK for the first request is not reached at client side.

https://github.sec.samsung.net/RS7-IOTIVITY/IoTivity/pull/383
(cherry picked from commit f6dfbd5194a482f2611a7b23c904dd4f7533c809)

Change-Id: I97968ae99a0abca39eb1bbe860cbfe73f684a738
Signed-off-by: Harish Kumara M <h.marappa@samsung.com>
Signed-off-by: Amit KS <amit.s12@samsung.com>