Add thread names for worker and master threads
Add thread names for worker and master threads

These thread names show up in gdb on modern systems
(el6.5 and later, recent Ubuntu, etc).

Change-Id: I049b0239b60f8129b44bba6514bf5821937a447d
Reviewed-on: http://gerrit.ent.cloudera.com:8080/1188
Reviewed-by: Henry Robinson <3eca10f30041813f045165784e24b5a950a6cc7e@cloudera.com>
Tested-by: Henry Robinson <3eca10f30041813f045165784e24b5a950a6cc7e@cloudera.com>

brockn/squeasel,danburkert/squeasel,brockn/squeasel,brockn/squeasel,danburkert/squeasel,brockn/squeasel,brockn/squeasel,danburkert/squeasel,brockn/squeasel,danburkert/squeasel,danburkert/squeasel,danburkert/squeasel