Switching to an unused tap device

It appears that if we use a tap device that has already been configured
by another test, then we cannot effectively change the configuration of
that device. Because for this test we need to rename the device, make
sure that we use an unallocated tap device.

Signed-off-by: Andrew Laucius <[email protected]>

Author: andrewla

tests/integration_tests/functional/test_snapshot_basic.py

@@ -606,10 +606,11 @@ def test_snapshot_rename_interface(uvm_nano, microvm_factory):
     Test that we can restore a snapshot and point its interface to a
     different host interface.
     """
-    base_iface = net_tools.NetIfaceConfig.with_id(0)
+    # We start at an unused tap index to avoid conflicts with other tests.
+    base_iface = net_tools.NetIfaceConfig.with_id(7)
 
     vm = uvm_nano
-    iface1 = dataclasses.replace(base_iface, tap_name="tap1")
+    iface1 = dataclasses.replace(base_iface, tap_name="tap8")
     vm.add_net_iface(iface=iface1)
     # Create an interface but don't attach it to the device
     vm.start()