Ensure the value of filter parameter is unicode
Ensure the value of filter parameter is unicode

To get rid of the warning message from sqlalchemy about non-unicode string.
This patch converts the value of filter parameter as unicode.

Change-Id: I1a842988ae3355cd2885b89f43f38bc1372d0907

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