Add addtl requirement used for configure.yml

Instruct developers to install the `ipaddr` package on their local box for the configure playbook.

Without it, following this README, they'll get these error messages:

```
TASK: [collectd | Configure collectd network plugin] **************************
fatal: [c1-management] => {'msg': 'No module named ipaddr', 'failed': True}
fatal: [c1-management] => {'msg': 'No module named ipaddr', 'failed': True}
fatal: [c1-storage-z1] => {'msg': 'No module named ipaddr', 'failed': True}
fatal: [c1-storage-z1] => {'msg': 'No module named ipaddr', 'failed': True}
fatal: [c1-proxy] => {'msg': 'No module named ipaddr', 'failed': True}
fatal: [c1-proxy] => {'msg': 'No module named ipaddr', 'failed': True}
fatal: [c1-storage-z3] => {'msg': 'No module named ipaddr', 'failed': True}
fatal: [c1-storage-z3] => {'msg': 'No module named ipaddr', 'failed': True}
fatal: [c1-storage-z2] => {'msg': 'No module named ipaddr', 'failed': True}
fatal: [c1-storage-z2] => {'msg': 'No module named ipaddr', 'failed': True}

FATAL: all hosts have already failed -- aborting
```