Mark sql_connection with secret flag

sql_connection contains the password in some setups and marking as
secret prevents accidental logging

fixes bug 1160680

Change-Id: Ib2d00219ea40a010c62e6a29045309f030e6de28
(cherry picked from commit f79915ec1d975219719e0ba99128d7c62398ae0a)
Merge "Mark sql_connection with secret flag" into stable/grizzly