code cleanup.

code cleanup.

This commit included code cleanup.
1. coding idiom
2. double free.
3. warning.
4. unlock

second patch included
change the mutex_unlock in NSProviderInterface.

Change-Id: Iff615c577f0cb0e868fa29c1592c523c9bed4d6f
Signed-off-by: jaesick.shin <jaesick.shin@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/9679
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Uze Choi <uzchoi@samsung.com>