[VOL-3142] Add config parameters to enable/disable tracing and set target jaeger agent for tracing data push

Also, added helper methods to assist correct Span creation by other Voltha code files.

Change-Id: Id6d312706d4c026aae02bb28f24ee2cae61e275b
diff --git a/go.mod b/go.mod
index dfd7d4d..0cc8432 100644
--- a/go.mod
+++ b/go.mod
@@ -36,7 +36,7 @@
 	github.com/spf13/pflag v1.0.3 // indirect
 	github.com/stretchr/testify v1.4.0
 	github.com/uber/jaeger-client-go v2.23.1+incompatible
-	github.com/uber/jaeger-lib v2.2.0+incompatible
+	github.com/uber/jaeger-lib v2.2.0+incompatible // indirect
 	go.etcd.io/etcd v0.0.0-20190930204107-236ac2a90522
 	go.uber.org/atomic v1.4.0 // indirect
 	go.uber.org/multierr v1.2.0 // indirect