Set hbase table_prefix default to None
Set hbase table_prefix default to None

...table_prefix default value was empty string which fails the connection to hbase thrift server. it should be set to None instead...

Change-Id: I1339c7dad09d311f0a4e3b16d67057e3471e8c5b
Fixes: bug #1173205
(cherry picked from commit 8bcc3773ac0153f69e56508a17abf465d90492a0)

shootstar/ctest,shootstar/ctest