m/p/common: use protobuf.Timestamp in NodeStatus

This updates NodeStatus to use google.protobuf.Timestamp.
See: issue #129.

Change-Id: I7902908a885a909d5ad6e232333037add5fb02e2
Reviewed-on: https://review.monogon.dev/c/monogon/+/831
Tested-by: Jenkins CI
Reviewed-by: Sergiusz Bazanski <serge@monogon.tech>
diff --git a/metropolis/test/launch/cluster/cluster.go b/metropolis/test/launch/cluster/cluster.go
index 0c85fc3..b3049e3 100644
--- a/metropolis/test/launch/cluster/cluster.go
+++ b/metropolis/test/launch/cluster/cluster.go
@@ -912,7 +912,7 @@
 		if cs.Status == nil {
 			continue
 		}
-		if cs.Status.Timestamp > is.Status.Timestamp {
+		if cs.Status.Timestamp.AsTime().Sub(is.Status.Timestamp.AsTime()) > 0 {
 			break
 		}
 		time.Sleep(time.Second)