Bump pbr minimum version, to avoid testrepository requirement

Change-Id: I89154466cb8a0a3f777df2cea48ae1812f3de881
diff --git a/requirements.txt b/requirements.txt
index 6318a59..6e8e1c1 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
-pbr>=0.5.21,<1.0
+pbr>=1.1.0
 
 argparse
 PyYAML>=3.1.0