Description of problem:
nodes that are used in overcloud that was deployed by a plan X are "available" for assignment in plan B

Version-Release number of selected component (if applicable):
openstack-tripleo-ui-7.4.3-0.20171023133305.8616195.el7ost.noarch

How reproducible:
always

Steps to Reproduce:
1. register, introspect nodes, assign nodes to roles in a default plan and deploy
2. create additional plan  and switch to it
3. on a plans page, check the amount of available node for assignment

Actual results:
3 nodes are available for assignment , 1 node assigned to compute and 1 to controller

Expected results:
0 available nodes for assignment 

Additional info:
default plan was used to deploy ovecloud with 3 controllers and 2 compute nodes.
$ nova list
+--------------------------------------+--------------+--------+------------+-------------+------------------------+
| ID                                   | Name         | Status | Task State | Power State | Networks               |
+--------------------------------------+--------------+--------+------------+-------------+------------------------+
| bbe96dc7-900c-4e00-bf48-3e86f10644d8 | compute-0    | ACTIVE | -          | Running     | ctlplane=192.168.24.16 |
| 92961354-a6c5-4158-afc9-6afcca1b190f | compute-1    | ACTIVE | -          | Running     | ctlplane=192.168.24.8  |
| 0f7f9be9-2cc3-4e17-b75b-df3c658609f4 | controller-0 | ACTIVE | -          | Running     | ctlplane=192.168.24.13 |
| def01bba-18c0-4c8c-b1d4-9bd29134bb21 | controller-1 | ACTIVE | -          | Running     | ctlplane=192.168.24.14 |
| ff32bb67-8240-4a4f-ab38-5ebccc506fa6 | controller-2 | ACTIVE | -          | Running     | ctlplane=192.168.24.17 |
+--------------------------------------+--------------+--------+------------+-------------+------------------------+


On UI, all nodes are in state active with profiles set (e.g compute and controller that were used in a default plan that was deployed)