conn: Remove assert on new listener connection when retrying

Opening a new listener connection can fail in many ways like a bind()
permission denied on a low port for instance.

And thus, we should expect to handle an error when creating a new one instead
of assert() on it.

To hit the removed assert:

  ORPort 80
  KeepBindCapabilities 0

Start tor. Then edit torrc:

  ORPort <some-IP>:80

HUP tor and the assert is hit.

Fixes #40073

Signed-off-by: David Goulet <dgoulet@torproject.org>
5 jobs for ticket40073_035_01 in 18 minutes and 29 seconds (queued for 2 seconds)
latest
Status Name Job ID Coverage
  Test
passed debian-distcheck #2052

00:06:19

passed debian-docs #2053

00:03:39

passed debian-hardened #2051

00:16:30

passed debian-integration #2054

00:07:08

passed debian-minimal #2050

00:05:15