devstack: Only run ovsdb-server/add-remote on nodes running the agent
devstack: Only run ovsdb-server/add-remote on nodes running the agent

In a multi-node devstack, particularly the Vagrant setup for OVN,
we do not run OVS on the control nodes. Thus, we cannot run
"ovsdb-server ovsdb-server/add-remote" on the controller node.

Change-Id: I1641bf9caefde6e01e673f757ab60287b6958c0e
Signed-off-by: Kyle Mestery <9cfbda34e625c7b0454bcb19a48d07c46f9097d2@mestery.com>

fdebonneval/skydive,fdebonneval/skydive,fdebonneval/skydive