Fix certificate not JSON serializable with latest robot 3.x
Fix certificate not JSON serializable with latest robot 3.x

Resolves  openbmc/openbmc-test-automation#1792

Change-Id: I9c68b2fd788b50ad901d02268a5ee99a69e7aa1c
Signed-off-by: George Keishing <bef0a9ecac45fb57611777c8270153994e13fd2e@in.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation