Issues related to handling shared pool

[Levovar]

Describe the bug
Two issues were discovered during testing.
1: when you configure multiple shared pools, Device Plugin correctly fails to start, however, the pools are advertised to Device Manager with 0 resource each
2: after DP starts up with the correct config, the invalid resource pools never disappear from the Node API

To Reproduce
Steps to reproduce the behavior:

1. Add two pools prefixed with shared_ into the Device Plugins Configmap
2. Start the Device Plugin
3. Correct the Configmap to a valid config, restart the Device Plugin

Expected behavior
After step three now CPU pools are visible under the Node API from the previous, faulty config