zdtm: static/msgque test update

v2: msgque test removed from zdtm.sh (feature is not supported yet)

1) Added namesapce isolation
2) Added non-empty queue state before migration
3) Added one more backward message send (child send message back
after receiving one from parent).

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Andrey Vagin <avagin@gmail.com>