libsnapshot: Print merge completion ops

Once the daemon is terminated, print merge completion
ops and the total ops present in the COW file. This
will help to know if the merge operation was interrupted
and how many pending operations were done during
each reboot until merge is completed

Bug: 167409187
Test: Incremental and full OTA
Signed-off-by: Akilesh Kailash <akailash@google.com>
Change-Id: Ie33c840e80aaeca86f51adc8085cb4e306dca110