Use /var/log/crowbar/sledgehammer instead of /install-logs [1/2]

This is a come-back of an old commit.

Note that this depends on https://github.com/crowbar/crowbar/pull/1891

Crowbar-Pull-ID: 6dc60e5906b8eb9abe8b14cdbefea73a78ce6f4c

Crowbar-Release: pebbles