[RESTAPI] Update submodule

Commits included:

1. Update API description for default vrf and ecmp routes
    fad87fa20f6b15e28c90e02a131c44d236d6a751

2. Fix WS-2018-0594 potential non-random UUIDs security issue
    8d4fd4a56b637d3b7403c321aef36b8dff58cd62

3. Add BFD config to subinterface and neighbor
    d3e8b8e4aee278fa11d7d86acabdab3fffc70d5a

4. Default Vrf static route support
    6cfc8fe110c46a1ee5a8430e02a440b5a7b4006d

5. Added flag to make go/pkg/ folder writable (removable)
    ee887c785c10d8b4f70db90ca50cc398327c5d73