Remove ZUUL_PIPELINE

Removing old ZUUL_ env variables which have been replaced with
Ansible variables.

Change-Id: I6496caca4bac86e12ff06d14f921ec8f9aafe825
diff --git a/tests/unit/test_scheduler.py b/tests/unit/test_scheduler.py
index 7ae0bd1..5fecfbe 100755
--- a/tests/unit/test_scheduler.py
+++ b/tests/unit/test_scheduler.py
@@ -913,11 +913,11 @@
         self.waitUntilSettled()
 
         for build in self.builds:
-            if build.parameters['ZUUL_PIPELINE'] == 'check':
+            if build.pipeline == 'check':
                 build.release()
         self.waitUntilSettled()
         for build in self.builds:
-            if build.parameters['ZUUL_PIPELINE'] == 'check':
+            if build.pipeline == 'check':
                 build.release()
         self.waitUntilSettled()