Modify the incorrect UUID parse in 'GetSubjectFromQueryString' API.

Modify the incorrect UUID parse in 'GetSubjectFromQueryString' API.

[NOTE]
GetSubjectFromQueryString API will be invoked when received REST requests to
retrieves the 'subject' field.
BTW, Since the subject of query is the string type,
The subject field should not be copied directly.
it should be converted as OicUuid_t.

[Patch #1] : Intial upload
[Patch #2] : Update unittest

Change-Id: I772ee91a9061ac2c9762ed09c5d09c5e90be90ff
Signed-off-by: Chul Lee <chuls.lee@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/8343
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Randeep Singh <randeep.s@samsung.com>