This patch adds a new parasite command, which unmaps the parasite blob.
This command never returns and the criu process traps the target process
on the exit from the munmap syscall.

v2: rename the function for unmaping a parasite blob to not intersects
with criu's functions.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>