MINOR: ssl: Add the "show ssl cert foo.pem.ocsp" CLI command

MINOR: ssl: Add the "show ssl cert foo.pem.ocsp" CLI command

Add the ability to dump an OCSP response details through a call to "show
ssl cert cert.pem.ocsp". It can also be used on an ongoing transaction
by prefixing the certificate name with a '*'.
Even if the ckch structure holds an ocsp_response buffer, we still need
to look for the actual ocsp response entry in the ocsp response tree
rather than just dumping the ckch's buffer details because when updating
an ocsp response through a "set ssl ocsp-response" call, the
corresponding buffer in the ckch is not updated accordingly. So this
buffer, even if it is not empty, might hold an outdated ocsp response.