TEP is part of old and new TZ when tz is updated after del-manager

TEP is part of old and new TZ when tz is updated after  del-manager

Issue observed:
1. TZA was present and TEPs were part of it.
2. ovsdb connection is removed by running delete-manager command on
switch
3. Change transport-zone of TEPs from TZA to TZC
4. ovsdb connection is set again by running set-manager command on
switch
5. TEPs go under teps-not-hosted since TZC is not yet present. It is
noted here that TEPs are still part of TZA in ITM config DS.
6. TZC is created from northbound
7. TEPs are moved from teps-not-hosted to TZC.
8. In the end, TEPs are part of TZA and TZC both. This is issue.

Fix provided:
When TEPs add notification come again with updated TZC, then
check if same TEP (key: dpid) is already present in any other TZ.
If present, then remove TEP from old TZ and then add TEP into newly
configured TZ.

Signed-off-by: Nishchya Gupta <nishchyag@altencalsoftlabs.com>
Change-Id: I98c3c89f70e60676ea9c5f73d90b1a750943e7a5