Re-enable the duplicate_pipeline test

Created separate class for it to use the new config in fixtures
named 'duplicate-pipeline'.

Also, modified it to use the new history assertion.

Change-Id: If6d9ac502122de1022efbebf91abd83f947b940e
diff --git a/tests/fixtures/config/duplicate-pipeline/main.yaml b/tests/fixtures/config/duplicate-pipeline/main.yaml
new file mode 100755
index 0000000..ba2d8f5
--- /dev/null
+++ b/tests/fixtures/config/duplicate-pipeline/main.yaml
@@ -0,0 +1,6 @@
+- tenant:
+    name: tenant-duplicate
+    source:
+      gerrit:
+        config-repos:
+          - common-config