Allow override of python-brick-cinderclient-ext library used by cinder

Added to requirements:
https://review.openstack.org/309084

Functional tests were added
https://review.openstack.org/265811

But they still use the version of python-brick-cinderclient-ext from pip.

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

Change-Id: I6d0f09950ea1200d3367a53aa4a3eea9be7abc66
Needed-by: I34f3b5ceaad7a50b1e9cadcc764f61c0aabe086d
diff --git a/tests/test_libs_from_pypi.sh b/tests/test_libs_from_pypi.sh
index a979c34..bb58088 100755
--- a/tests/test_libs_from_pypi.sh
+++ b/tests/test_libs_from_pypi.sh
@@ -42,7 +42,7 @@
 ALL_LIBS+=" debtcollector os-brick automaton futurist oslo.service"
 ALL_LIBS+=" oslo.cache oslo.reports osprofiler"
 ALL_LIBS+=" keystoneauth ironic-lib neutron-lib oslo.privsep"
-ALL_LIBS+=" diskimage-builder os-vif"
+ALL_LIBS+=" diskimage-builder os-vif python-brick-cinderclient-ext"
 
 # Generate the above list with
 # echo ${!GITREPO[@]}