Update error handling logic in EnrolleeSecurity.

Update error handling logic in EnrolleeSecurity.

 - OCSecure::discoverSingleDevice API is updated with another return value.(https://gerrit.iotivity.org/gerrit/#/c/17361/)
   According that patch, EnrolleeSecurity::discoverTargetSecureResource api is updated additional error handling logic.

Change-Id: If0e9c2e1000c1c754386c77f204a7bdd5bd0923b
Signed-off-by: Parkhi <h_w.park@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/17363
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>