Encode datadir for xtrabackup
Encode datadir for xtrabackup

Xtrabackup previously used a hardcoded datadir.  In the latest
update to xtrabackup, the my.cnf config option datadir is now
parsed.  This variable was unset, causing galera to implode.

backport: liberty

Change-Id: I523d1989575dbe24a891fcae3b6bf56d83e69615
Closes-Bug: #1509281

toby82/kolla,dardelean/kolla-ansible,stackforge/kolla,negronjl/kolla,toby82/kolla,coolsvap/kolla,limamauricio/mykolla,toby82/kolla,coolsvap/kolla,negronjl/kolla,coolsvap/kolla,rahulunair/kolla,tonyli71/kolla,GalenMa/kolla,mrangana/kolla,openstack/kolla,openstack/kolla,dardelean/kolla-ansible,mrangana/kolla,intel-onp/kolla,nihilifer/kolla,nihilifer/kolla,mandre/kolla,mandre/kolla,GalenMa/kolla,limamauricio/mykolla,dardelean/kolla-ansible,tonyli71/kolla,intel-onp/kolla,limamauricio/mykolla,stackforge/kolla,mandre/kolla,rahulunair/kolla,stackforge/kolla,negronjl/kolla