dabba: refactor sock filter parser return path.
dabba: refactor sock filter parser return path.

This refactoring makes the sock filter parser return proper error code
and a single return statement.

Signed-off-by: Emmanuel Roullit <e51ad7dcb99c77ecf30f537962c562ac80636eba@gmail.com>

eroullit/dabba,eroullit/dabba,eroullit/dabba,eroullit/dabba