Update certificate path validation logic
Update certificate path validation logic

This change adds "Digital Signature" as a required "critical Key Usage"
bit in root and intermediate CA certificates.

Change-Id: I95052e9b2625b79edfc158aee9e0681c151b521b
Signed-off-by: Kishen Maloor <c62ddea3cd661a9268bff15f07fc2229cdc9ac02@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/27759

iotivity/iotivity-constrained,iotivity/iotivity-constrained,iotivity/iotivity-constrained,iotivity/iotivity-constrained