UI: reduce test execution speed for remove tests

1) There was no issue, I realized we were waiting for 20 sec unnecessarily for each remove test and for each ddt test, where in we where searching for the deleted entity.
2) I have added a timeout of 5 sec for the subnet_remove as an example.
3) we can do the same for other entities and its remove tests.
4) we can raise an issue and track this for all the other entities.
5) This fix should save atleast 1min for each remove test which is ddt. 
6) Hope this will speed up the UI automation further :)