Cache OCSP request fail for 5 minutes and display a better error (#2)

[FabienChaynes]

(#2)

This PR improves the SSL revocation test.

Sometimes, when we query the OCSP responder, we get a failure. Currently this failure is not cached so we will keep querying the OCSP responder (which might be temporary down).

This PR improves this by caching the error for 5 minutes, so that we won't put more load on the OCSP responder if he's not working properly at the moment.
In addition to that, the error message returned was improved in this situation to explain with it failed and to include the OCSP responder URI.

Here's what the error will look like now:

irb(main):001:0> SSLTest.test("https://cloudreports.xyz")
=> [true, "OCSP test couldn't be performed: OCSP response request failed (OCSP URI: http://isrg.trustid.ocsp.identrust.com, error: Wrong response type (Net::HTTPServiceUnavailable))", #<OpenSSL::X509::Certificate: subject=#<OpenSSL::X509::Name CN=cloudreports.xyz>, issuer=#<OpenSSL::X509::Name CN=Let's Encrypt Authority X3,O=Let's Encrypt,C=US>, serial=#<OpenSSL::BN:0x0000000006baf620>, not_before="2020-03-10T03:25:33.000Z", not_after="2020-06-08T03:25:33.000Z">]

[jarthod]

I have the version before you changed it on my machine so I changed the matcher so work with both