Allow override of os-brick library used by cinder

os-brick code was pulled out of cinder and made into its own library
https://review.openstack.org/#/c/155552/

added to requirements:
https://review.openstack.org/#/c/177372/

Integration tests were added
https://review.openstack.org/#/c/188156/

But they still use the version of os-brick from pip.

This change updates devstack to pull in the changes from
os-brick patch sets instead, when configured to do so.

Needed-by: Id2bc10782847861fe4bb5e9e46245654450e38fd

Change-Id: I5359dd37dfe94bd469d5ca35f9fbaeda61b5fac4
diff --git a/lib/cinder b/lib/cinder
index da22e29..b8cf809 100644
--- a/lib/cinder
+++ b/lib/cinder
@@ -39,6 +39,7 @@
 
 # set up default directories
 GITDIR["python-cinderclient"]=$DEST/python-cinderclient
+GITDIR["os-brick"]=$DEST/os-brick
 CINDER_DIR=$DEST/cinder
 
 # Cinder virtual environment
@@ -381,6 +382,13 @@
 
 # install_cinder() - Collect source and prepare
 function install_cinder {
+    # Install os-brick from git so we make sure we're testing
+    # the latest code.
+    if use_library_from_git "os-brick"; then
+        git_clone_by_name "os-brick"
+        setup_dev_lib "os-brick"
+    fi
+
     git_clone $CINDER_REPO $CINDER_DIR $CINDER_BRANCH
     setup_develop $CINDER_DIR
     if [ "$CINDER_ISCSI_HELPER" = "tgtadm" ]; then