KVM: move post-shutdown cleanup operations
KVM: move post-shutdown cleanup operations

Currently putting the cleanup just after the actual shutdown ensures
that it never gets called, due to how the retry/shutdown cycle works.
So we move those cleanups to their new dedicated place.

Signed-off-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>
Reviewed-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>

dimara/ganeti,leshchevds/ganeti,bitemyapp/ganeti,yiannist/ganeti,grnet/snf-ganeti,onponomarev/ganeti,mbakke/ganeti,andir/ganeti,apyrgio/snf-ganeti,andir/ganeti,andir/ganeti,ganeti/ganeti,dimara/ganeti,ganeti-github-testing/ganeti-test-1,onponomarev/ganeti,ganeti/ganeti,mbakke/ganeti,leshchevds/ganeti,apyrgio/ganeti,apyrgio/ganeti,bitemyapp/ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,grnet/snf-ganeti,mbakke/ganeti,yiannist/ganeti,ganeti/ganeti,apyrgio/snf-ganeti,leshchevds/ganeti