xenapi: Fix rescue

commit 4389f2292a0177c8eedc0a398ceb3c5535a9ef82 appears to have broken
rescue on xenapi. The xenapi driver requires the actual image id to be
in the "image_meta" parameter to the rescue driver.

bug 1227350

Change-Id: Ifce27ab26eb5f998850faeefe5f21a4705439821
Merge "xenapi: Fix rescue"