ssa.c: Fix handling port error in downstream thread

In case of port error device event, in addition to closing
smdb, prdb listen sockets and all downstream open connections,
proper file descriptors should be cleaned, so that downstream
thread rpoll will not listen to them.

Signed-off-by: Ilya Nelkenbaum <ilyan@mellanox.com>
Signed-off-by: Hal Rosenstock <hal@mellanox.com>