[tests] Fix failures when openwisp-controller is accompanied by openwisp-monitoring

[nemesifier]

Possible alternative to openwisp/openwisp-monitoring#282.

We can fix the tests of openwisp-controller which fail when openwisp-monitoring is installed by changing the conditions of the tests.

Some of the tests are failing because they expect 1 templates but 2 are found because openwisp-monitoring creates a template. Failures like these can be fixed easily by changing the conditions (eg: count the templates at the beginning of the test, ensure there's 1 template more at the end).