Revert "Fixing neutron::server deprecated warnings"

This reverts commit b799640d219b42955165bd81acde5b32ee0f99f9.

Change-Id: I978cd75b8264e1b5234fc930d4488fff513fe53e
Fixing neutron::server connection parameter

Previously, neutron::server's (deprecated) sql_connection parameter
had a default value, preventing the new/preferred connection
parameter from ever being used.

This change removes that default, permitting the connection
parameter to work properly, and extends unit tests to confirm.

bug introduced at commit 82552e79316a4ffc1c879dd3aaa1f4735a4a35a0,
change I300fc12092bca1abdd105e0c0c272f7fd49258ac

Change-Id: I116b482c620b5c44b88c1b801438a100343f6f9f
(cherry picked from commit af1fd0b6042c76fc48bae81d36a74b7a51d00fb7)
Merge "Revert "Fixing neutron::server deprecated warnings"" into stable/havana
Merge "Fixing neutron::server connection parameter" into stable/havana