tests: py: add vlan test case for ip/inet family

tests: py: add vlan test case for ip/inet family

before fixup, this failed with:

line 4: 'add rule ip test-ip4 input vlan id 1': '[ payload load 2b @ link header + 12 => reg 1 ]' mismatches '[ payload load 2b @ link header + 0 => reg 1 ]'

... because the auto-dependency did not add the preceeding ethernet
header, so vlan was using the wrong offset.

Note than vlan id match in inet input families will only work if header
removal was disabled, i.e.

... add link vethin1 name vethin1.3 type vlan id 3 reorder_hdr off

otherwise, kernel will strip the vlan tag and interface appears as
a normal ethernet interface.

Signed-off-by: Florian Westphal <fw@strlen.de>