fix: allow active revocation on http revoke endpoint

[VonRehberg]

Name of feature: Allow active revocation via http endpoint

Pain or issue this feature alleviates: active revocation was already possible via cli but not via http

[hslatman]

Hey @VonRehberg, thank you for the PR.

Can you remove the test at

certificates/api/revoke_test.go

Lines 46 to 53 in af2e58a

	"error/non-passive not implemented": {
	rr: &RevokeRequest{
	Serial: "10",
	ReasonCode: 8,
	Passive: false,
	},
	err: &errs.Error{Err: errors.New("non-passive revocation not implemented"), Status: http.StatusNotImplemented},
	},

?

From the looks of it the change looks OK. It seems to stem from the time we only supported passive revocation, but since then support for active revocation was added by the community. In practice the way that is configured and works does seem to make the Passive boolean obsolete, and it seems to be just informational at the moment. I think there's improvements that can be done, but that would require some more work to feed it through, and doesn't need to be in this PR.