Commit 3d835f7d

 made two incorrect assumptions that
lead to instance moves failing for plain instances.
- The Import/Export interface is available at the level
  of block devices, not (as was assumed in the said
  commit) at the level of configuration objects.
- The Import/Export functions provide an argv vector
  not a single string; also the quoted version thereof
  is not a parameter so be substituted into a shell
  template (the quoted string does contain several
  characters with special meaning to the shell, e.g.,
  spaces).
Fix this now.

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Hrvoje Ribicic <riba@google.com>