Add new oslo.privsep library to oslo repos

A new project olos.privsep has been created but failes sdvm testing as
even though the library is added ro PROJECTS and LIBS_FROM_GIT it isn't
installed by devstack.

Add oslo.privsep to the install_oslo function

Change-Id: Ia4d56747d56dcfe50889ebbdf9d553df13e1b950
diff --git a/stackrc b/stackrc
index 4026ff8..819aa01 100644
--- a/stackrc
+++ b/stackrc
@@ -371,6 +371,10 @@
 GITREPO["oslo.policy"]=${OSLOPOLICY_REPO:-${GIT_BASE}/openstack/oslo.policy.git}
 GITBRANCH["oslo.policy"]=${OSLOPOLICY_BRANCH:-master}
 
+# oslo.privsep
+GITREPO["oslo.privsep"]=${OSLOPRIVSEP_REPO:-${GIT_BASE}/openstack/oslo.privsep.git}
+GITBRANCH["oslo.privsep"]=${OSLOPRIVSEP_BRANCH:-master}
+
 # oslo.reports
 GITREPO["oslo.reports"]=${OSLOREPORTS_REPO:-${GIT_BASE}/openstack/oslo.reports.git}
 GITBRANCH["oslo.reports"]=${OSLOREPORTS_BRANCH:-master}