Do not assume order of pci slot list

This fixes the neutron.tests.unit.sriovnicagent.test_eswitch_manager
.TestEmbSwitch.test_get_pci_list unit test that breaks with a
randomized PYTHONHASHSEED (see the bug report).

The test assumed that the pci slot list was sorted, so sort
the result before comparing.

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: Ia2d879cc1251fb9cf9b653a41064e902b30005af
Partial-bug: #1348818
Merge "Do not assume order of pci slot list"