Bump pbr requirment to 0.5.21

Removes the need for setuptools_git. Also, change the upper bound,
as the next planned release will be 1.0 and we'd like to coordinate
that move.

Change-Id: I9a9ff8c62f800da3bf02d4afb3bc24ddfd0d24d5

global-requirements.txt

@@ -36,7 +36,7 @@ paramiko>=1.8.0
 passlib
 Paste
 PasteDeploy>=1.5.0
-pbr>=0.5.16,<0.6
+pbr>=0.5.21,<1.0
 pecan>=0.2.0
 pip>=1.0
 PrettyTable>=0.6,<0.8
@@ -67,7 +67,6 @@ PyYAML>=3.1.0
 qpid-python
 requests>=1.1
 Routes>=1.12.3
-setuptools_git>=0.4
 simplejson>=2.0.9
 six
 sockjs-tornado>=1.0.0,<2.0.0

update.py

@@ -55,7 +55,7 @@ _setup_py_text = """#!/usr/bin/env python
 import setuptools
 
 setuptools.setup(
-    setup_requires=['pbr>=0.5.20'],
+    setup_requires=['pbr>=0.5.21,<1.0'],
     pbr=True)
 """