Fixed memory leaks while using Tizen CAPI

Fixed memory leaks while using Tizen CAPI

wifi_ap_get_ip_address() returns string with allocated memory, this
patch frees the memory if it was allocated earlier.
wifi_ap_get_essid() returns string with allocated memory, this patch
frees the memory after its use

Change-Id: Ieb6adbabca8317ab66f0efddf8635d4a1693c662
Signed-off-by: Saurav Babu <saurav.babu@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/5157
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>