xen: block BootableTestCase from py34 testing
xen: block BootableTestCase from py34 testing

The tests use mox which isn't stable with py34 testing, there are
race failures with the assertions. This test fails in unexpected
ways in unrelated changes so we need to blacklist it from py34
testing.

Change-Id: Ieb972f4705254af4b014d79a39bd6d78ad0b6376
Closes-Bug: #1526369

CEG-FYP-OpenStack/scheduler,cyx1231st/nova,vmturbo/nova,mikalstill/nova,klmitch/nova,dims/nova,sebrandon1/nova,Juniper/nova,cloudbase/nova,rajalokan/nova,phenoxim/nova,klmitch/nova,mikalstill/nova,cernops/nova,cyx1231st/nova,NeCTAR-RC/nova,sebrandon1/nova,bigswitch/nova,alaski/nova,zhimin711/nova,rajalokan/nova,jianghuaw/nova,gooddata/openstack-nova,dims/nova,BeyondTheClouds/nova,CEG-FYP-OpenStack/scheduler,BeyondTheClouds/nova,jianghuaw/nova,openstack/nova,klmitch/nova,rahulunair/nova,openstack/nova,openstack/nova,cloudbase/nova,Juniper/nova,gooddata/openstack-nova,mikalstill/nova,vmturbo/nova,hanlind/nova,mahak/nova,jianghuaw/nova,cloudbase/nova,mahak/nova,sebrandon1/nova,vmturbo/nova,mahak/nova,jianghuaw/nova,cernops/nova,zhimin711/nova,hanlind/nova,BeyondTheClouds/nova,klmitch/nova,rajalokan/nova,vmturbo/nova,Juniper/nova,rajalokan/nova,phenoxim/nova,gooddata/openstack-nova,alaski/nova,rahulunair/nova,bigswitch/nova,gooddata/openstack-nova,cernops/nova,hanlind/nova,NeCTAR-RC/nova,rahulunair/nova,Juniper/nova