Add pbr to devstack.

It's being used in all of the core projects, so we should install it
at the start so we can ensure that we don't break everything all at
once.

Change-Id: I326d724264803e88315ee9e40f4634836baf6e0b
diff --git a/stack.sh b/stack.sh
index 32a7d74..63a87b9 100755
--- a/stack.sh
+++ b/stack.sh
@@ -273,6 +273,7 @@
 
 # Set the destination directories for OpenStack projects
 OPENSTACKCLIENT_DIR=$DEST/python-openstackclient
+PBR_DIR=$DEST/pbr
 
 
 # Interactive Configuration
@@ -610,6 +611,10 @@
 
 echo_summary "Installing OpenStack project source"
 
+# Install pbr
+git_clone $PBR_REPO $PBR_DIR $PBR_BRANCH
+setup_develop $PBR_DIR
+
 # Install clients libraries
 install_keystoneclient
 install_glanceclient