rename _vtocc, _vts and _mysql in vitess server

Rename _vtocc, _vts and _mysql ports in the portmap to vt, vts and mysql.
Merge pull request #224 from youtube/replication

Replication
Merge pull request #217 from yaoshengzhe/fix_portmap_naming

rename _vtocc, _vts and _mysql in vitess server