feature: Add option to rebalance VMs by their assigned resources. [#16]

Fixes: #16

.changelogs/1.0.0/16_add_rebalancing_by_assigned_resources.yml

@@ -0,0 +1,2 @@
+added:
+  - Add option to rebalance by assigned VM resources to avoid overprovisioning. [#16]

README.md

@@ -85,6 +85,7 @@ The following options can be set in the `proxlb.conf` file:
 | api_pass | FooBar | Password for the API. |
 | verify_ssl | 1 | Validate SSL certificates (1) or ignore (0). (default: 1) |
 | method | memory | Defines the balancing method (default: memory) where you can use `memory`, `disk` or `cpu`. |
+| mode | used | Rebalance by `used` resources (efficiency) or `assigned` (avoid overprovisioning) resources. (default: used)|
 | balanciness | 10 | Value of the percentage of lowest and highest resource consumption on nodes may differ before rebalancing. (default: 10) |
 | ignore_nodes | dummynode01,dummynode02,test* | Defines a comma separated list of nodes to exclude. |
 | ignore_vms | testvm01,testvm02 | Defines a comma separated list of VMs to exclude. (`*` as suffix wildcard or tags are also supported) |
@@ -101,6 +102,7 @@ api_pass: FooBar
 verify_ssl: 1
 [balancing]
 method: memory
+mode: used
 # Balanciness defines how much difference may be
 # between the lowest & highest resource consumption
 # of nodes before rebalancing will be done.