[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/go.etcd.io/bbolt/boltsync_unix.go b/vendor/go.etcd.io/bbolt/boltsync_unix.go
new file mode 100644
index 0000000..9587afe
--- /dev/null
+++ b/vendor/go.etcd.io/bbolt/boltsync_unix.go
@@ -0,0 +1,8 @@
+// +build !windows,!plan9,!linux,!openbsd
+
+package bbolt
+
+// fdatasync flushes written data to a file descriptor.
+func fdatasync(db *DB) error {
+	return db.file.Sync()
+}