selftests: netdevsim: sprinkle more udevadm settle

Number of tests are failing when netdev renaming is active
on the system. Add udevadm settle in logic determining
the names.

Fixes: 242aaf03 ("selftests: add a test for ethtool pause stats")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240114224726.1210532-1-kuba@kernel.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>