ci: Don't install kamaki from wheezy repos

Install always the lates kamaki. This is needed because we may want to
install a kamaki that supports new features but hasn't been release yet
(i.e. isn't stable enough). Instead we upload it to the unstable repo.

ci/schemas/one_node_wheezy/wheezy.conf

@@ -57,6 +57,6 @@ snf-image = wheezy
 snf-network = wheezy
 python-objpool = wheezy
 nfdhcpd = wheezy
-kamaki = wheezy
+kamaki =
 python-bitarray = wheezy
 python-nfqueue = 0.4+physindev-1~wheezy