SCTP: Always flush the queue when uncorcking.

When the code calls uncork, trigger a queue flush, even
if the queue was not corked.  Most callers that explicitely
cork the queue will have additinal checks to see if they 
corked it.  Callers who do not cork the queue expect packets
to flow when they call uncork.

The scneario that showcased this bug happend when we were not
able to bundle DATA with outgoing COOKIE-ECHO.  As a result
the data just sat in the outqueue and did not get transmitted.
The application expected a response, but nothing happened.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>