Bug 1391 - New DataBroker unexpected behaviour

* deleted empty override for checkWriteApplicable() in
NormalizedNodeContainerModificationStrategy and added check for node
being created by another transaction in checkWriteApplicable()
in SchemaAwareApplyOperation.
* updated concurrency tests.

Change-Id: I0fd5fb230014f794897a30d1a45a86b61a3a8378
Signed-off-by: Jan Hajnar <jhajnar@cisco.com>
Merge "Bug 1391 - New DataBroker unexpected behaviour"