Remove tests omission from coverage target in tox.ini
Remove tests omission from coverage target in tox.ini

In coverage target in tox.ini, there is the following argument:
  --omit="watcher/tests/*"

However, in .coveragerc, the tests are also omitted,
according to line 4 in .coveragerc:
  omit = watcher/tests/*

So the watcher/tests/* directory is omitted twice. As it can be
seen in other modules (e.g.: swift, nova) omitting only in
.coveragerc should be enough.

Change-Id: I72951196a346fb73a90c998138fc91dd171432cd
Closes-Bug: #1552617

stackforge/watcher,openstack/watcher,openstack/watcher,stackforge/watcher