Do not assume order of convert_kvp_list_to_dict method responses

Do not assume order of convert_kvp_list_to_dict method responses

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

The test assumed that the convert_kvp_list_to_dict method from
neutron.api.v2.attributes returned elements in a particular
order. Found with PYTHONHASHSEED=1.

The fix refactors the test case to handle unsorted responses from
convert_kvp_list_to_dict.

[1] neutron.tests.unit.api.v2.test_attributes.TestConvertKvp

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: I864904db1428b88c482ad17a69b33e876a8d042c