Create external network for advertised routes tests

Due to the fact that public network is configured as shared external
network and shared among all the tests it leads to the situation if
during advertised routes tests any of test will add floatingip this
floating IP will appear in advertised routes. To avoid this each test
creates it's own public network used in the test therefore only
routes created by these tests will appear in this network.

Related-PRODX: PRODX-30128
Change-Id: Icf85f84c8d0ba43e5b1c0578360817f0fd809039
1 file changed