Add field FileSHA in BasicDigest struct

[aledbf]

No description provided.

[k8s-reviewable]

This change is 

[coveralls]

Coverage decreased (-0.04%) to 44.071% when pulling 8deca37 on aledbf:auth-sha into 65e8cec on kubernetes:master.

[aledbf]

ping @jcmoraisjr

[jcmoraisjr]

About the commit: adding the FileSHA field is fine and fixes the reload.

Any idea to the false positive and annoying warning below whenever changing a non cert/key pair or a CA secret?

 func (ic *GenericController) syncSecret(key string) {
     glog.V(3).Infof("starting syncing of secret %v", key)
     cert, err := ic.getPemCertificate(key)
     if err != nil {
         glog.Warningf("error obtaining PEM from secret %v: %v", key, err)
         return
     }