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
1 file changed