net: tcp: Invalid transition from FIN_WAIT_1 to CLOSE_WAIT

We incorrectly changed the state from FIN_WAIT_1 to CLOSE_WAIT.
This caused ACK be sent in CLOSE_WAIT state when the connection
was closed by peer. Sending ACK in this state is not allowed
according to RFC. The connection was still closed but slightly
wrong way.

Jira: ZEP-1961

Change-Id: Ie4aa6818128d4190230b679e26ac9630c7d45d69
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>