[PKT_SCHED]: act_api: Fix module leak while flushing actions

Module reference needs to be given back if message header
construction fails.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>