Separate Certgen Secret and Job Reconciliation

[danehans]

Please describe the problem you have The operator should only create the certgen Job if the contourcert and envoycert secrets do not exist.

xref: https://github.com/projectcontour/contour-operator/pull/31

/cc @jpeach @Miciah

[jpeach]

Taking this a bit further, the operator should generate and track unique names for these certificates.

[Miciah]

This may no longer be relevant once we resolve https://github.com/projectcontour/contour-operator/issues/34.