fixes #2468 locates the correct server certificate for enrollments

[andrewpmartinez]

• determines certificate for signing based on all identity server certs
• does not cache as certificates may reload

[qrkourier]

Creating a router failed for some reason in one of the checks:

error: error creating edge-routers instance in Ziti Edge Controller at [https://ziti-controller-client.zititest.svc.cluster.local:443/edge/management/v1.](https://ziti-controller-client.zititest.svc.cluster.local/edge/management/v1.) Status code: 500 Internal Server Error, Server returned: {
    "error": {
        "cause": {
            "code": "UNHANDLED",
            "message": "could not get enrollment signer: could not determine enrollment signer: could not find a configured server certificate that matches hostname [miniziti-controller.192.168.49.2.sslip.io]"
        },
        "code": "UNHANDLED",
        "message": "An unhandled error occurred",
        "requestId": "Rm8fHn1oJ"
    },
    "meta": {
        "apiEnrollmentVersion": "0.0.1",
        "apiVersion": "0.0.1"
    }
}