fix test_flavors_extra_specs failure

tempest.api.compute.admin.test_flavors_extra_specs.FlavorsExtraSpecsTestXML
failed due to test_flavor2 already exists

Fixing Bug 1220034

Change-Id: I259f4202978ac20d341349d1d227c6ef14c31d9b
Merge "fix test_flavors_extra_specs failure"