HotStuff Client - avoid quorum call to execute a command

[hanish520]

• Currently HotStuff client is sends a command to all the servers in the configuration through a gorums quorum call ExecCommand.

• Instead clients should use multicast to send the command to the servers.

• This removes the overhead on servers to send responses to the clients for every command executed.

• Servers now add an additional api to provide the status of the client commands.

• To implement the above api, servers might have to maintain an additional data structure to maintain status for client commands.