Merge pull request #147 from vedujoshi/master

Merge commits 01a8ffe and 76cbe3d
Harden test_crud tests

* Sometimes in a /24 subnet, picking a random ip for a port used to
choose an IP which is already created. So, use /16 subnet to be more
deterministic
* Use right variable in a log message
* Avoid deleting an already deleted object (router/subnet/port/network)