refactor code and separate client as an standalone connector

Signed-off-by: Clark Wang <clark.wangs@gmail.com>
rename sub connector

Signed-off-by: Clark Wang <clark.wangs@gmail.com>
restore test

Signed-off-by: Clark Wang <clark.wangs@gmail.com>
allow init different type of redis connector

Signed-off-by: Clark Wang <clark.wangs@gmail.com>