Block /30, /31, /32 on neutron server

This patch is a forward-port of a change to puppet-coe-service-patch
that deals with assuring that very small subnet masks aren't used
on networks created by neutron.  The patch is partly related to
upstream bug #1341040 for which the community has
adopted a different and less strict approach. We have opted
for a stricter approach, so we'll need to carry this patch for now.
The original commit message follows:

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commit 8dabd46a2f9827e9b10dfe3461a986392ad7d82f
Author: Pauline Yeung <yeungp@cisco.com>
Date:   Thu Jul 24 15:45:07 2014 -0700

    DE631 block /30 in neutron server, in addition to blocking in CLI and
    dhcp an addition to blocking in CLI and dhcp agent.

    Change-Id: If405e49b8faa4c6a584441ee93dab211a8f521e6
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Partial-bug: #1341040
Partial-rally-bug: rally-bug DE631
Partial-rally-bug: rally-bug DE494
Implements: rally-user-story US4145
Implements: rally-task TA3473
Not-in-upstream: true