Modify GetVolumeList so output on stderr from lvs doesn't break it.
Modify GetVolumeList so output on stderr from lvs doesn't break it.

Reviewed-by: imsnah



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