Fix PYTHONHASHSEED bugs in test_security_groups_rpc

Fix PYTHONHASHSEED bugs in test_security_groups_rpc

This fixes the test_security_group_member/rule_updated unit tests[1]
that breaks with a randomized PYTHONHASHSEED (see the bug report).

The test assumed that several dictionaries had elements in a
particular order. Found with PYTHONHASHSEED=2.

The fix refactors the test case by injecting values using the same
ordering[2].

[1] neutron.tests.unit.agent.test_securitygroups_rpc.\
   TestSecurityGroupAgentWithOVSIptables

[2] https://github.com/openstack/neutron/blob/\
   e8364a72e62d83e5a76bec1d7aa76ecfe2ed53ac/\
   neutron/tests/unit/agent/test_securitygroups_rpc.py#L1630-L1635

Partial-bug: #1348818

Note: There are several other unrelated unit tests that also break with
a randomized PYTHONHASHSEED, but they are not addressed here. They will
be addressed in separate patches.

Change-Id: I5077764045a34d1be0e85bb4b80f3655e87692cc