Pipe: Drop connect_seq increase line

Pipe: Drop connect_seq increase line

Revert commit 0fc47e267b6f8dcd4511d887d5ad37d460374c25.

When accepting and "connect.connect_seq == existing->connect_seq",
existing->state maybe STATE_OPEN, STATE_STANDBY or STANDY_CONNECTING.
This commit only fix partial problem and want to assert
"(existing->state == STATE_CONNECTING)".

So later we added codes to catch
"(existing->state == STATE_OPEN || existing->state == STATE_STANDBY)"
before asserting.

Backport: dumpling, firefly, giant

Signed-off-by: Haomai Wang <haomaiwang@gmail.com>