Add last_error usage to deploy and teardown methods

Change I7e079627b87b2cb1606e677e287dd08dcc87263a introduce new
'last_error' field in nodes table. This patch add saving error
messages in this field for do_node_deploy and do_node_tear_down
methods of conductor.

Change-Id: I9aaab42c1e91568ab6a4657df4fe972441e3ac6d
Merge "Add last_error usage to deploy and teardown methods"