LUSetNodeParams: Don't break config on mc demotion.
LUSetNodeParams: Don't break config on mc demotion.

If --force is used to demote an MC, but then there are not enough MCs in
the cluster, the configuration gets corrupted until a node is promoted.

In order to avoid that we only allow demotion with --force if the node
is offlined or drained at the same time, and we don't have any other
node available to promote.

Signed-off-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>
Reviewed-by: Olivier Tharan <0947fcc917eb1d3c89ad818beb61e3b2c3cf3bba@google.com>

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