btrfs: test if receive with qgroups corrupts metadata

btrfs: test if receive with qgroups corrupts metadata

This test case does some concurrent send/receives with qgroups
enabled.  Currently (4.14-rc7) this usually results in btrfs check
errors, and often also results in a WARN_ON in
record_root_in_trans().

Bisecting points to 6426c7ad697d (btrfs: qgroup: Fix qgroup
accounting when creating snapshot) as the culprit.

Signed-off-by: Justin Maggard <jmaggard@netgear.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>