Revert "libsnapshot: Partially implement OpenSnapshotWriter."

Revert "Link to libsnapshot_cow everywhere libsnapshot is linked."

Revert submission 1433573-vab-libsnapshot-linkage

Reason for revert: b/169981170, update crash for droidfooders.
Reverted Changes:
Ie75bba98c:Link to libsnapshot_cow where libsnapshot is linke...
Ieedfadc55:libsnapshot: Partially implement OpenSnapshotWrite...
I28a5d4a88:Link to libsnapshot_cow everywhere libsnapshot is ...

Exempt-From-Owner-Approval: Revert to unblock dogfood
Change-Id: I0677df77672aca9fd54d94e009ac0be7c88a1a9d