Fix for Jira [IOT-1424]

Fix for Jira [IOT-1424]

1. Modified CHPGetOCContentType() and CHPGetOptionID() to
internally duplicate the string parameter passed and
work on this copy, thereby maintaining const correctness.
2. Also modified unit test to pass "application/cbor" as
http content type.

Change-Id: Ic0ea5704ddff20dc67086296e54775ef8d677d69
Signed-off-by: Veeraj Khokale <veeraj.sk@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/13013
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Ashok Babu Channa <ashok.channa@samsung.com>
(cherry picked from commit cac65bc77127b61056783bdd1178263518682912)
Reviewed-on: https://gerrit.iotivity.org/gerrit/15275
Tested-by: jenkins-iotivity <jenkins@iotivity.org>
Reviewed-by: Phil Coval <philippe.coval@osg.samsung.com>
Reviewed-by: Kevin Kane <kkane@microsoft.com>
Reviewed-by: Uze Choi <uzchoi@samsung.com>