veyron/runtimes/google/lib/publisher: We should finish unmounting before claiming we are done.

Change-Id: I16585ecf07515bcce30df375381cdb1278f9cff9
diff --git a/runtimes/google/lib/publisher/publisher.go b/runtimes/google/lib/publisher/publisher.go
index b6e8d31..25db23f 100644
--- a/runtimes/google/lib/publisher/publisher.go
+++ b/runtimes/google/lib/publisher/publisher.go
@@ -156,8 +156,8 @@
 		case cmd := <-cmdchan:
 			switch tcmd := cmd.(type) {
 			case stopCmd:
-				close(donechan)
 				state.unmountAll()
+				close(donechan)
 				vlog.VI(2).Info("ipc pub: exit runLoop")
 				return
 			case addServerCmd: