Make x509 unittest testClockSkew a bit less flaky

Since the tested function actually uses time.time(), it cannot be make
fully stable, but 1 second is very dangerous; let's just test SKEW * 2
and higher since that should be good (if the delta between _GenCert
and VerifyX509Certificate is 5 minutes, then…).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>

test/ganeti.utils.x509_unittest.py

@@ -195,7 +195,7 @@ class TestCertVerification(testutils.GanetiTestCase):
       self.assertEqual(result, (None, None))
 
     # skew too great, not accepting certs
-    for before in [SKEW + 1, SKEW * 2, SKEW * 10]:
+    for before in [SKEW * 2, SKEW * 10]:
       cert = self._GenCert(key, before, validity)
       (status, msg) = utils.VerifyX509Certificate(cert, 1, 2)
       self.assertEqual(status, utils.CERT_WARNING)