In xc_domain_save ensure that we signal completion at the end of each
batch.

This ensures that the next logged line starts on a new line. e.g. instead of:
     Savefile contains xl domain config
    xc: Saving memory: iter 3 (last sent 0 skipped 0): 0/32768    0%migration target: Transfer complete, requesting permission to start domain.
    migration sender: Target has acknowledged transfer.
what is desired is:
     Savefile contains xl domain config
    xc: Saving memory: iter 0 (last sent 0 skipped 0): 32768/32768  100%
    xc: Saving memory: iter 1 (last sent 32576 skipped 192): 32768/32768  100%
    xc: Saving memory: iter 2 (last sent 217 skipped 0): 32768/32768  100%
    xc: Saving memory: iter 3 (last sent 0 skipped 0): 32768/32768  100%
    migration target: Transfer complete, requesting permission to start domain.
    migration sender: Target has acknowledged transfer.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>