VOL-1381 and VOL-1091 Add feature to collect PMmetrics of OLT, this will collect Tx and Rx and posts to kafka. This commit is also related to changes of commit 72b25abd4e804596413558ef10f098c2262dd65d voltha-go
Updated review comments

Updated with code optimization
Updated with dep files
Updated fix for sanity test
Updated with gomod changes

Change-Id: I899e855812a6eda812c64664a9154321cdb16876
diff --git a/mocks/mockCoreProxy.go b/mocks/mockCoreProxy.go
index 874c13a..48ad4e0 100644
--- a/mocks/mockCoreProxy.go
+++ b/mocks/mockCoreProxy.go
@@ -201,3 +201,8 @@
 	}
 	return nil
 }
+
+// DevicePMConfigUpdate implements mock DevicePMConfigUpdate
+func (mcp *MockCoreProxy) DevicePMConfigUpdate(ctx context.Context, pmConfigs *voltha.PmConfigs) error {
+	return nil
+}