Replace gets function

Replace gets function

gets() function does not check for buffer length
and always results in a vulnerability.

Change-Id: I74abbe3f8a746513bb955455891ab1ca4746f1a7
Signed-off-by: ch79.cho <ch79.cho@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/12395
Reviewed-by: JungYong KIM <jyong2.kim@samsung.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
(cherry picked from commit 74ab7a7ff852baab940fd9367cf1b7dbd63a2369)
Reviewed-on: https://gerrit.iotivity.org/gerrit/12465