libsnapshot: Don't call RemoveAllSnapshots on normal boot.

This change was made when hardening recovery against libsnapshot bugs,
but was too aggressive. It's causing gsid to start, and due to an issue
in libgsid, get retained indefinitely. Dial it back a bit.

Bug: 397325642
Test: boot, ps -A | grep gsid
Change-Id: If013eb1d9082ca1f98bc4f3a26209af38b07e1cc