Merge branch 'mirror-to-gretap-tests'

Petr Machata says:

====================
Test mirror-to-gretap with bridge in UL

This patchset adds more tests to the mirror-to-gretap suite where bridge
is present in the underlay. Specifically it adds tests for bridge VLAN
handling, FDB, and bridge port STP status.

In patches #1-#3, the codebase is refactored to support the new tests.

In patch #4, an STP test is added to the mirroring library, that will
later be called from bridge tests.

In patches #5-#8, the test for mirror-to-gretap with an 802.1q bridge in
underlay is adapted and more tests are added.

In patch #9, an STP test is added to the test suite for mirror-to-gretap
with an 802.1d bridge in underlay.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>