This patch fixes a couple of issues caused by change-id:
I15d20ce5292b70f0c2b4ba55c1f1318181481596
Changes to the code for when the ext_tx experiment is not enabled
were merged from master but as var_tx does not exist on master
the changes had not been applied to the case when var_tx experiment
is enabled

Change-Id: Iaf2b717e6b8626b2b6a03226127221b776b49884