Do not assume order of security group rules

Do not assume order of security group rules

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

The test assumed that the security_group_rules_for_devices method from
neutron.agent.securitygroups_rpc returned security group rules in a
particular order. Found with PYTHONHASHSEED=2.

The fix refactors the test case to handle unsorted security group rules.

[1] neutron.tests.unit.plugins.ml2.test_security_group.\
    TestMl2SGServerRpcCallBack.\
    test_security_group_rules_for_devices_ipv4_ingress_addr_pair

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: I1b2bd4100c19004f12822c414aefc86aae9849db