[DyConf][Daemon] Test case for set followed by a delete

Summary: Test case for set followed by a delete.

Test Plan:
```
$ bin/gocov test -deps -exclude-goroot github.com/gow/dyconf/daemon | tee /tmp/qqq | bin/gocov report
ok    github.com/gow/dyconf/daemon  0.827s

github.com/gow/dyconf/config/index.go  indexBlock.find     100.00% (6/6)
github.com/gow/dyconf/config/index.go  getKeyHash      100.00% (5/5)
github.com/gow/dyconf/config/config.go   ConfigFile.Get      100.00% (4/4)
github.com/gow/dyconf/config/header.go   configHeader.SetVersion   100.00% (2/2)
github.com/gow/dyconf/config/header.go   configHeader.SetRecordCount   100.00% (2/2)
github.com/gow/dyconf/config/errors.go   Error.GetErrorString    100.00% (1/1)
github.com/gow/dyconf/config/header.go   configHeader.UpdateTime   100.00% (1/1)
github.com/gow/dyconf/config/header.go   configHeader.NumRecords   100.00% (1/1)
github.com/gow/dyconf/config/config.go   ConfigFile.Delete     100.00% (1/1)
github.com/gow/dyconf/config/errors.go   Error.Error       100.00% (1/1)
github.com/gow/dyconf/config/errors.go   Error.GetErrorNo    100.00% (1/1)
github.com/gow/dyconf/config/header.go   configHeader.Version    100.00% (1/1)
github.com/gow/dyconf/config/config.go   NewWritable       100.00% (1/1)
github.com/gow/dyconf/config/index.go  indexBlock.set      90.00% (9/10)
github.com/gow/dyconf/config/config.go   ConfigFile.Set      81.25% (13/16)
github.com/gow/dyconf/config/errors.go   Error.ErrorString     71.43% (5/7)
github.com/gow/dyconf/config/index.go  indexBlock.delete     71.43% (5/7)
github.com/gow/dyconf/config/index.go  indexBlock.get      71.43% (5/7)
github.com/gow/dyconf/config/data.go   dataBlock.set       66.67% (4/6)
github.com/gow/dyconf/config/config.go   initWithProtOptions     60.00% (9/15)
github.com/gow/dyconf/config/data.go   dataBlock.get       60.00% (3/5)
github.com/gow/dyconf/config/utils.go  createFile      58.33% (7/12)
github.com/gow/dyconf/config/header.go   configHeader.print    0.00% (0/6)
github.com/gow/dyconf/config/config.go   New         0.00% (0/1)
github.com/gow/dyconf/config/header.go   configHeader.ByteSize     0.00% (0/1)
github.com/gow/dyconf/config/header.go   configHeader.ModifiedTime   0.00% (0/1)
github.com/gow/dyconf/config/index.go  indexRecord.print     0.00% (0/1)
github.com/gow/dyconf/config/index.go  indexBlock.print    0.00% (0/1)
github.com/gow/dyconf/config/utils.go  ConfigFile.PrintIndexBlock  0.00% (0/1)
github.com/gow/dyconf/config/utils.go  ConfigFile.PrintHeaderBlock   0.00% (0/1)
github.com/gow/dyconf/config     ---------------------------   69.60% (87/125)

github.com/gow/dyconf/daemon/server.go   httpServer.httpCallbackSet  100.00% (14/14)
github.com/gow/dyconf/daemon/server.go   httpServer.httpCallbackDelete   100.00% (7/7)
github.com/gow/dyconf/daemon/server.go   httpServer.httpCallbackGet  100.00% (6/6)
github.com/gow/dyconf/daemon/errors.go   Error.GetErrorString    100.00% (5/5)
github.com/gow/dyconf/daemon/server.go   sendHttpError       100.00% (4/4)
github.com/gow/dyconf/daemon/server.go   httpServer.stop     100.00% (4/4)
github.com/gow/dyconf/daemon/server.go   sendHttpJSONResponse    100.00% (2/2)
github.com/gow/dyconf/daemon/daemon.go   dyconfDaemon.stop     100.00% (1/1)
github.com/gow/dyconf/daemon/errors.go   Error.GetErrorNo    100.00% (1/1)
github.com/gow/dyconf/daemon/server.go   httpServer.start    90.00% (18/20)
github.com/gow/dyconf/daemon/daemon.go   dyconfDaemon.init     84.62% (11/13)
github.com/gow/dyconf/daemon/main.go   main        0.00% (0/8)
github.com/gow/dyconf/daemon/errors.go   Error.Error       0.00% (0/1)
github.com/gow/dyconf/daemon     -----------------------------   84.88% (73/86)

```

Reviewers: tommy.testy

Reviewed By: tommy.testy

Differential Revision: D44
Merge branch 'master' of github.com:gow/dyconf