[VOL-3142] Update dependency of voltha-lib-go to include log package registration fix

Change-Id: I36890c7aa685e46721b481d5c965f9c0bc86934c
diff --git a/vendor/github.com/opentracing/opentracing-go/.gitignore b/vendor/github.com/opentracing/opentracing-go/.gitignore
new file mode 100644
index 0000000..c57100a
--- /dev/null
+++ b/vendor/github.com/opentracing/opentracing-go/.gitignore
@@ -0,0 +1 @@
+coverage.txt