Implement test that checks invalid cert case

Signed-off-by: Dimitris Karakasilis <dimitris@karakasilis.me>

cmd/discovery/client/client.go

@@ -17,6 +17,7 @@ import (
 )
 
 var errPartNotFound error = fmt.Errorf("pass for partition not found")
+var errBadCertificate error = fmt.Errorf("unknown certificate")
 
 func NewClient() (*Client, error) {
 	conf, err := unmarshalConfig()
@@ -103,10 +104,15 @@ func (c *Client) waitPass(p *block.Partition, attempts int) (pass string, err er
 			tries = 0
 			continue
 		}
+
 		if generated { // passphrase is encrypted
 			return c.decryptPassphrase(pass)
 		}
 
+		if err == errBadCertificate { // No need to retry, won't succeed.
+			return
+		}
+
 		if err == nil { // passphrase available, no errors
 			return
 		}