v2 deduplication: add separate function for punch to use on restore

Signed-off-by: Tikhomirov Pavel <snorcht@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
v2 deduplication: add auto-dedup on restore

if option --auto-dedup is set on restore, then as soon as page is
restored it will be punched from the image.

open image in O_RDWR mode

Signed-off-by: Tikhomirov Pavel <snorcht@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
v2 test: auto-deduplication on restore

Signed-off-by: Tikhomirov Pavel <snorcht@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
v2 test: auto-dedup on restore

Use maps04, on tmpfs, check if size of pages image is zero in the end

Signed-off-by: Tikhomirov Pavel <snorcht@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
deduplication: add --auto-dedup option description

Signed-off-by: Tikhomirov Pavel <snorcht@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>