[swsssdk-py] update submodule for sonic-py-swsssdk (#3826)

update multiDB changes in sonic-py-swsssdk, including:
*[multi-DB] Part 4: add sonic-db-cli to replace redis-cli (#54)
*[multi-DB] Part 3: Python API changes (#52)
*remove SonicV2Connector which is not used any more (#53)

This needs #3825 to be merged first. Otherwise when reloading minigraph/config will hit error.

Signed-off-by: Dong Zhang d.zhang@alibaba-inc.com