Add delimiter to block key

[robbrockbank]

Partial fix for: https://github.com/projectcalico/calicoctl/issues/1631

[robbrockbank]

I think this is required. Looking at the logs, the key does not include the terminating "/", so we need to include it in our key construction.

However, the logs also indicated that the block branch was never being hit (and I've tested that code in isolation and it seems fine) - so I also think that the 0.11.1 confd in our calico/node may not have been the correct build. This is speculation.

Logs:

2017-05-08T23:31:26Z rlb-kdd-with-routing-rpqr confd[74]: DEBUG Getting key /calico/ipam/v2/host/rlb-kdd-with-routi
ng-rpqr/ipv4/block
2017-05-08T23:31:26Z rlb-kdd-with-routing-rpqr confd[74]: DEBUG map[]

[caseydavenport]

LGTM - let me know how the testing goes :)