[CONPRO-1429] 100% CPU usage by iotivity stack

[CONPRO-1429] 100% CPU usage by iotivity stack

Here before the max number of observers was 255 and when more
than 255 observers were there an infinite loop was running.
Increasing the number of observers and changing the logic so
that infinite loop should not be run when observer count reaches
max number of observers.

https://github.sec.samsung.net/RS7-IOTIVITY/IoTivity/commit/3f9cb8af60cd5ed929ed876d95e82f2650309f9c
(cherry picked from 3f9cb8af60cd5ed929ed876d95e82f2650309f9c)

Change-Id: Ib0bb86817d2dbf8c2d5f5806cb49ffa2e002cd21
Signed-off-by: DoHyun Pyun <dh79.pyun@samsung.com>