Fix inconsistent update type during concurrent P4Runtime writes

This is achieved by optimistically updating the P4Runtime mirror using
the write request (instead of waiting for a response) and by serializing
building write requests for the same device.

This change requires updating the P4Runtime protocol classes to expose
the content of the write request.

It also includes:
- force member weight to 1 when reading groups (some server
implementation still fails to be compliant to the spec)
- remove unused operation timeout handling in GDP (now all RPCz have a
timeout)

Change-Id: Ib4f99a6085c1283f46a2797e0c883d96954e02e9
diff --git a/core/api/src/main/java/org/onosproject/net/pi/runtime/PiActionProfileGroup.java b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiActionProfileGroup.java
index 57e65a2..3fd7e08 100644
--- a/core/api/src/main/java/org/onosproject/net/pi/runtime/PiActionProfileGroup.java
+++ b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiActionProfileGroup.java
@@ -125,7 +125,7 @@
         return MoreObjects.toStringHelper(this)
                 .add("actionProfile", actionProfileId)
                 .add("id", groupId)
-                .add("members", members)
+                .add("members", members.values())
                 .add("maxSize", maxSize)
                 .toString();
     }