inspect_cow: Add an --extract-to argument.

This adds an --extract-to argument to inspect_cow to verify that full
OTA snapshots contain correct data. It does not yet work for ordered
ops.

Test: inspect_cow
Bug: N/A
Change-Id: I9014da3e83fd4fb5ea54ac1d36e527b3e3e6c9d5

Change-Id: I7e256e8ddec626980cdcf8680bbeac3c2e9d8de1
1 file changed