[Tachyon-74] : Add free of in-memory file/folder from CLI"
- A new CLI is added Eg: ./bin/tachyon tfs free [file/folder path]
- This CLI command will free the in-memory blocks for file/folder.
Fix unit test case for free command with a sleap of HB interval.
Fix the assert condition in the unit test case. Test performed, and passed.
Merge pull request #533 from Huawei-Tachyon/jira74

Tachyon-74 : Add free of in-memory file/folder from CLI