[VOL-2235] Mocks and interfaces for rw-core

This update consists of mocks that are used by the rw-core
during unit testing.  It also includes interfaces used for unit
tests.

Change-Id: I20ca1455c358113c3aa897acc6355e0ddbc614b7
diff --git a/vendor/github.com/modern-go/concurrent/.gitignore b/vendor/github.com/modern-go/concurrent/.gitignore
new file mode 100644
index 0000000..3f2bc47
--- /dev/null
+++ b/vendor/github.com/modern-go/concurrent/.gitignore
@@ -0,0 +1 @@
+/coverage.txt