Pin pepper >= 0.5.2 and <0.5.4

Login is broken in 0.5.4, need to pin to older version,
till bug is resolved.

Change-Id: I87212bb6d613eef1e4a12763e929f89004e54774
Related-Prod: https://mirantis.jira.com/browse/PROD-18188
diff --git a/src/com/mirantis/mk/Python.groovy b/src/com/mirantis/mk/Python.groovy
index 10236b5..eb4b19c 100644
--- a/src/com/mirantis/mk/Python.groovy
+++ b/src/com/mirantis/mk/Python.groovy
@@ -311,7 +311,8 @@
     def common = new com.mirantis.mk.Common()
 
     // virtualenv setup
-    requirements = ['salt-pepper>=0.5.2']
+    // pin pepper till https://mirantis.jira.com/browse/PROD-18188 is fixed
+    requirements = ['salt-pepper>=0.5.2,<0.5.4']
     setupVirtualenv(path, 'python2', requirements, null, true, true)
 
     // pepperrc creation