[IOT-2121] [IOT-2116] Fix CTT "message mac does not match"

[IOT-2121] [IOT-2116] Fix CTT "message mac does not match"

Test case CT1.7.2.1-2 from CTT v1.5.6 fails with "message mac does
not match":
- After CTT successfully posted the owner credential
- While trying to establish a new DTLS session, using the new
credential

Change-Id: I282632d1071c76afba629081d6853d376c347473
Signed-off-by: Dan Mihai <Daniel.Mihai@microsoft.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/19515
Reviewed-by: Kevin Kane <kkane@microsoft.com>
Reviewed-by: Nathan Heldt-Sheller <nathan.heldt-sheller@intel.com>
Tested-by: Nathan Heldt-Sheller <nathan.heldt-sheller@intel.com>