Get rid of flake8 compatibility issues due to pbr

The version of pbr package should stay between a restricted
range so that flake8 gate will work as expected.
Details: http://sprunge.us/RDVV?log (L: 92)

Change-Id: Ifeb52fbac28dac40b894923c727b60d56768976d

requirements.txt

@@ -1,4 +1,4 @@
-pbr>=0.10
+pbr>=0.10,<1.0
 iso8601
 eventlet
 netaddr>=0.7.6
@@ -9,4 +9,4 @@ Babel>=1.3
 oauthlib
 netifaces
 PyYAML
-tzlocal
+tzlocal

setup.py

@@ -15,5 +15,5 @@
 import setuptools
 
 setuptools.setup(
-    setup_requires=['pbr>=0.10'],
+    setup_requires=['pbr>=0.10,<1.0'],
     pbr=True)