Digital Loggers Inc. PDU configurations are dependent between machines

[ptylenda]

System information:
$ uname -a
Linux gklab-188-200 4.8.0-37-generic #39-Ubuntu SMP Thu Jan 26 02:27:07 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

$ dpkg -l '*maas*'|cat
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-===============================-==============================-============-=================================================
ii maas 2.1.3+bzr5573-0ubuntu1~16.10.1 all "Metal as a Service" is a physical cloud and IPAM
ii maas-cli 2.1.3+bzr5573-0ubuntu1~16.10.1 all MAAS client and command-line interface
un maas-cluster-controller <none> <none> (no description available)
ii maas-common 2.1.3+bzr5573-0ubuntu1~16.10.1 all MAAS server common files
ii maas-dhcp 2.1.3+bzr5573-0ubuntu1~16.10.1 all MAAS DHCP server
ii maas-dns 2.1.3+bzr5573-0ubuntu1~16.10.1 all MAAS DNS server
ii maas-proxy 2.1.3+bzr5573-0ubuntu1~16.10.1 all MAAS Caching Proxy
ii maas-rack-controller 2.1.3+bzr5573-0ubuntu1~16.10.1 all Rack Controller for MAAS
ii maas-region-api 2.1.3+bzr5573-0ubuntu1~16.10.1 all Region controller API service for MAAS
ii maas-region-controller 2.1.3+bzr5573-0ubuntu1~16.10.1 all Region Controller for MAAS
un maas-region-controller-min <none> <none> (no description available)
un python-django-maas <none> <none> (no description available)
un python-maas-client <none> <none> (no description available)
un python-maas-provisioningserver <none> <none> (no description available)
ii python3-django-maas 2.1.3+bzr5573-0ubuntu1~16.10.1 all MAAS server Django web framework (Python 3)
ii python3-maas-client 2.1.3+bzr5573-0ubuntu1~16.10.1 all MAAS python API client (Python 3)
ii python3-maas-provisioningserver 2.1.3+bzr5573-0ubuntu1~16.10.1 all MAAS server provisioning libraries (Python 3)

Issue description and steps to reproduce:

This has been observer while using Digital Loggers Inc. PDU in Power settings for machines.
1. Connect a few machines to MAAS. In this description let's say we have machines A, B, X, Y
2. Set power configuration for machines A and B so that they are assigned to web powerswitch with IP 10.0.0.1
3. Set power configuration for machines X and Y so that they are assigned to web powerswitch with IP 10.0.0.2
4. Due to some problems you have to move machine B from powerswitch 10.0.0.1 to 10.0.0.2
5. Introduce these changes in MAAS machines configuration
6. When you change power settings for machine B, all machines using powerswitch 10.0.0.1 will be affected
7. This results in all machines A, B, X, Y being assigned to powerswitch 10.0.0.2, which is not intended because we wanted to have machine A @ 10.0.0.1 and B, X, Y @ 10.0.0.2.

This makes any changes in power settings troublesome if you use more than 1 web powerswitch. When you have to move a machine between powerswitches, many other machines are affected in MAAS and it results in wrong configuration.