remove unused Exceptions in WorkerStorage
format code
Merge pull request #488 from shimingfei/RemoveUnusedExceptions

remove unused Exceptions in WorkerStorage and format the code
set jetty thread count to 9

Set jetty thread count from 5 to 9 to avoid the bug mentioned in
[TACHYON-196]
Merge pull request #492 from PasaLab/TACHYON-196

[TACHYON-196] Set jetty thread count to 9