bug: volume server can't connect to master if master is started with ip=(null)

What steps will reproduce the problem?
1. delete raft's log
2. weed master (without any parameter)
3. weed volume will fail when trying to post to http://:9333/dir/join

What is the expected output? What do you see instead?
after step 2, enter http://localhost:9333/cluster/master, "Leader" is ":9333", 
which should be something like "127.0.0.1:9333"

What version of the product are you using? On what operating system?
windows XP 32-bit and 7 64-bit (both tested), 0.47. I confirmed that 0.46 works 
fine because it does have /client/status yet :)

Please provide any additional information below.
If master is started with something like -ip 127.0.0.1, everything's fine.
I've debugged a little bit and I think it's just that somewhere in raft you 
can't pass an empty addres.

Original issue reported on code.google.com by rujia....@gmail.com on 12 Mar 2014 at 4:57

varun2784 / weed-fs

bug: volume server can't connect to master if master is started with ip=(null) #64