cr-restore: fix error handling and memory leak in read_vma

CID 996203 (#1 of 1): Resource leak (RESOURCE_LEAK)
15. leaked_storage: Variable "vma" going out of scope leaks the storage it points to.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>