Add two new autocomputed vars to Nodes
Add two new autocomputed vars to Nodes

Currently we track the max disk usage/max vcpus as percentages, however
sometimes it's easier to check against minimum free disk or maximum
number of cpus, as units instead of percentages.

This patch adds two new variables, lo_dsk, hi_cpu, which are recomputed
whenever we change the m_dsk/m_cpu 'master' values.

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