Update documentation for sql_connection credentials

Lets use the same username and password the database server setups by
default.  Otherwise, following the examples will result in a password /
user mismatch.

Change-Id: Ieee67b5912bb823a3b422752bb7f7e30bbba4897
Signed-off-by: Paul Belanger <paul.belanger@polybeacon.com>
Merge "Update documentation for sql_connection credentials"