conpaas.core.clouds.ec2: convert volume size

git-svn-id: svn://svn.forge.objectweb.org/svnroot/contrail/trunk/conpaas@5238 ef35cc4a-2640-4bbf-98bc-65920db7d8ae
conpaas-xtreemfs: add toggle_persistent and set_osd_size methods

git-svn-id: svn://svn.forge.objectweb.org/svnroot/contrail/trunk/conpaas@5239 ef35cc4a-2640-4bbf-98bc-65920db7d8ae