[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/bolt_linux.go b/vendor/go.etcd.io/bbolt/bolt_linux.go
new file mode 100644
index 0000000..7707bca
--- /dev/null
+++ b/vendor/go.etcd.io/bbolt/bolt_linux.go
@@ -0,0 +1,10 @@
+package bbolt
+
+import (
+	"syscall"
+)
+
+// fdatasync flushes written data to a file descriptor.
+func fdatasync(db *DB) error {
+	return syscall.Fdatasync(int(db.file.Fd()))
+}