MINOR: ssl: Add certificate's path to certificate_ocsp structure

MINOR: ssl: Add certificate's path to certificate_ocsp structure

In order to have some information about the frontend certificate when
dumping the contents of the ocsp update tree from the cli, we could
either keep a reference to a ckch_store in the certificate_ocsp
structure, which might cause some dangling reference problems, or
simply copy the path to the certificate in the ocsp response structure.
This latter solution was chosen because of its simplicity.