Fix UpdateMaster issues

[lafengnan]

1. If server name was not configured in twemproxy conf, smitty will exit w/ index out of range error. To fix it I add a defense to make sure the server name has been set.
2. In ubuntu 12.04 the restart command does not work if it has arguments.
3. If the redis master and slave nodes are running in the same machine with different ports, the functionality of UpdateMaster will not work correctly.