Exclude cyborg tests dir in UT cover report

We don't care about coverage of actual test code, So exclude
cyborg/tests dir.

Change-Id: I534f652c098ed91afb8f52cfc6bb78268a4d5f21

.coveragerc

@@ -0,0 +1,12 @@
+[run]
+branch = True
+source = cyborg
+omit =
+    cyborg/tests/*
+    cyborg/hacking/*
+
+[report]
+ignore_errors = True
+exclude_lines =
+    @abc.abstract
+    raise NotImplementedError

.gitignore

@@ -2,7 +2,6 @@
 *.tox
 *.retry
 .coverage
-.coveragerc
 .coverage.*
 .venv
 .stestr/

.stestr.conf

@@ -1,3 +1,3 @@
 [DEFAULT]
-test_path=./
+test_path=./cyborg/tests
 top_dir=./