fix(rust): fix vault locking on nfs volumes
the lock file must be opened with read permissions
in order to obtain a shared lock on it.  Write permission is not
enough.  This was working on local filesystem but failed on attached
volumes on the cloud.
@@ -85,6 +85,7 @@ impl FileStorage {
fn open_lock_file(lock_path: &PathBuf) -> Result<File> {
std::fs::OpenOptions::new()
.write(true)
+ .read(true)
.create(true)
.open(lock_path)
.map_err(map_io_err)
