[VOL-1512] Set device ownership

This commit consists of the following:
1) Set device ownership per Core in a Core-pair such that only 1
Core actively process a device (i.e. handles all the requests for
that device) while the other Core in the pair passively watch for
updates on that device and will take over in case the owner Core
failed to process the transaction.
2) Cleanup the lock mechanisms to ensure we use a read lock when
needed instead of just a lock.
3) Update logical port additions such that ports are added only when
the device is enabled.
4) Update the port Ids for the logical ports.
5) Update some sarama client configs for performance - this is an
ongoing tune up.
6) Update the adapter request handler in the Core to send back an
ACK immediately to the adapter request instead of processing the
request fully and then sending an ACK.  This reduces the latency
over kafka and therefore reduces the likelihood of timeouts.

Change-Id: I9149bf3ba6fbad38e3a29c76ea8dba2f9f731d29
diff --git a/rw_core/utils/core_utils.go b/rw_core/utils/core_utils.go
new file mode 100644
index 0000000..1e1ed9f
--- /dev/null
+++ b/rw_core/utils/core_utils.go
@@ -0,0 +1,24 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package utils
+
+type DeviceID struct {
+	Id string
+}
+
+type LogicalDeviceID struct {
+	Id string
+}