Add comment on RPC client

void

init_rpc_client() {

    // Tests show that a margo instance initalized with MARGO_SERVER_MODE can

    // also be used in client mode. The documentation is unclear whether that is

    // intended behavior and what should be preferred. Since the current

    // approach with a separate Margo client works, I'll leave it like this for

    // now, but using only one Margo instance may be considered if problems

    // should arise.

    auto mid = margo_init(GKFS_DATA->bind_addr().c_str(), MARGO_CLIENT_MODE,

                          HG_TRUE, 0);

    if(mid == MARGO_INSTANCE_NULL) {