Fixed the test.

This test must prove that when the signature_certificate_file_list
has a path to the file system and urls, the file system path has high
priority over the urls.

slapos/libnetworkcachetests.py

@@ -198,7 +198,7 @@ class TestNetworkcacheClient(LibNetworkCacheMixin):
              shacache=self.shacache_url,
              shadir=self.shadir_url,
              signature_private_key_file=self.signature_private_key_file,
-             signature_certificate_file_list=['http://localhost:0/public.pem'])
+             signature_certificate_file_list=['http://localhost:0/public.pem',
+                                              self.signature_certificate_file])
     signature_string = nc._getSignatureString()
-    self.assertRaises(IOError, \
-                        nc._verifySignatureInCertificateList, signature_string)
+    self.assertTrue(nc._verifySignatureInCertificateList(signature_string))