TACHYON-198 Move UserConf usage to use TachyonConf

This PR consist next steps to integrate new configuration work:
-) Remove usage of UserConf
-) Push TachyonConf to Tachyon Hadoop's file system (aka TFS class).
-) Remove UserConf.java from repo.
It is not a blocker, I could punt it to different PR to help make it clear. This PR is primarily used to remove UserConf and integrate it with TachyonConf. There are limit on how many times for every programmer on how many times need to manually change the code, but apparently it was still under my patience limit so I did not make that structural change =P
As like your other comment about returning back the @ Before method I hope we could punt this one to different PR.