Do not assume order of network_uuid's

Do not assume order of network_uuid's

This fixes the neutron.tests.unit.test_linux_dhcp.TestDnsmasq
.test_existing_dhcp_networks unit test that breaks with a
randomized PYTHONHASHSEED (see the bug report).

The test assumed that the network_uuid's 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.

Partial-bug: #1348818
Change-Id: Ia6f742e1fae0687164b841beebb4efcf31ff2625