BMC fails after node is commissioned

[Chris Gregan]

Build Version/Date: MAAS Version 1.10.0 (+bzr4577)
Environment used for testing: Xenial with Trusty as the commissioning OS

Summary:
After discovery and commissioning access to the IPMI/BMC is lost and cannot be recovered

Steps to Reproduce:
1) Enlist node
2) Commission node
3) Attempt to deploy

Expected result:
Deployment is successful

Actual result:
Feb 5 06:35:36 dratini maas.power: [ERROR] Error changing power state (on) of node: brideless-marilynn (node-07dcf988-cbfa-11e5-8471-ecb1d78a353c)
Feb 5 06:35:36 dratini maas.node: [INFO] brideless-marilynn: Status transition from DEPLOYING to FAILED_DEPLOYMENT
Feb 5 06:35:36 dratini maas.node: [ERROR] brideless-marilynn: Marking node failed: Node could not be powered on: Could not authenticate to node's BMC: Invalid password.
Feb 5 06:35:57 dratini maas.node_query: [ERROR] brideless-marilynn: Error when checking power state: (b'UNHANDLED', 'Unknown Error [dratini:pid=17718:cmd=PowerQuery:ask=36]')
Feb 5 06:35:57 dratini maas.node_query: [INFO] brideless-marilynn: Unable to determine power state.
Feb 5 06:39:16 dratini maas.power: [ERROR] Power state could not be queried: Failed to power query 192.168.246.112:
Feb 5 06:39:17 dratini maas.power: [ERROR] brideless-marilynn: Failed to refresh power state: Failed to power query 192.168.246.112: