Remove invalid tests-py3 whitelist item
Remove invalid tests-py3 whitelist item

The tests for XenAPI plugins were introduced with change [1].
This change also appended them to the python3 test whitelist,
as the functionality could only be executed on python2.4 environment.
The aforementioned changes were removed with change [2], but
the whitelist item was left behind. This change removes the obsolete
line.

[1] 2aa81e9ef6d04f2fdf1c69e16ceeef156cefedfa
[2] 21149582ff944585fb0a815ebe9515c1ec38eb7f

Change-Id: Ibc15e9a06adf34512eda904d0bb3eba1eed04784

rajalokan/nova,rahulunair/nova,Juniper/nova,gooddata/openstack-nova,klmitch/nova,phenoxim/nova,jianghuaw/nova,gooddata/openstack-nova,openstack/nova,openstack/nova,rahulunair/nova,mahak/nova,klmitch/nova,gooddata/openstack-nova,Juniper/nova,vmturbo/nova,mahak/nova,vmturbo/nova,gooddata/openstack-nova,mikalstill/nova,mikalstill/nova,rajalokan/nova,mikalstill/nova,vmturbo/nova,jianghuaw/nova,Juniper/nova,rajalokan/nova,klmitch/nova,rahulunair/nova,vmturbo/nova,jianghuaw/nova,openstack/nova,Juniper/nova,rajalokan/nova,jianghuaw/nova,klmitch/nova,phenoxim/nova,mahak/nova