Introduce .coveragerc

We don't need the result of tempest/tests/* and tempest/openstack/*
coverage. This commit omits it with introducing .coveragerc.

Partially implements bp unit-tests

Change-Id: I0465d916e195e3d340dece24ac7b01a0fc13e5c1
diff --git a/.gitignore b/.gitignore
index 28a9b9c..1777cb9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,4 +16,5 @@
 build
 .testrepository
 .coverage*
+!.coveragerc
 cover/