Add oslo.service to devstack

Add the ability to switch on oslo.service master using
LIBS_FROM_GIT

Change-Id: I00fe7776aea005b6d4e0a84fce54f33a862b57e3
diff --git a/stackrc b/stackrc
index c16a999..1ac1338 100644
--- a/stackrc
+++ b/stackrc
@@ -382,6 +382,10 @@
 GITREPO["oslo.serialization"]=${OSLOSERIALIZATION_REPO:-${GIT_BASE}/openstack/oslo.serialization.git}
 GITBRANCH["oslo.serialization"]=${OSLOSERIALIZATION_BRANCH:-master}
 
+# oslo.service
+GITREPO["oslo.service"]=${OSLOSERVICE_REPO:-${GIT_BASE}/openstack/oslo.service.git}
+GITBRANCH["oslo.service"]=${OSLOSERVICE_BRANCH:-master}
+
 # oslo.utils
 GITREPO["oslo.utils"]=${OSLOUTILS_REPO:-${GIT_BASE}/openstack/oslo.utils.git}
 GITBRANCH["oslo.utils"]=${OSLOUTILS_BRANCH:-master}