hv_chroot: move unmount to CleanupInstance()
hv_chroot: move unmount to CleanupInstance()

This allows cleanup to be done properly if the "instance" wasn't running
at all (based on the CleanupInstance framework, instead of the retry in
hypervisor).

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

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