Fix verify-disks with broken volume groups
Fix verify-disks with broken volume groups

When a remote node returns invalid LVM data, we check it, but we don't
stop and continue with the rest of the checks (which require a valid
volume group). This raises an internal error and breaks verify disks.

This seems unchanged for a long while, I don't know why it surfaced just
recently.

Reviewed-by: ultrotter

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