tests: add setsockopt() output on Python 3

Python 3 appears to call setsockopt() where Python 2 did not.

Differential Revision: https://phab.mercurial-scm.org/D5652

tests/test-http-api.t

@@ -156,6 +156,7 b' Restart server with support for API serv'
   >     user-agent: test
   > EOF
   using raw connection to peer
+  s> setsockopt(6, 1, 1) -> None (py3 !)
   s>     GET /api HTTP/1.1\r\n
   s>     Accept-Encoding: identity\r\n
   s>     user-agent: test\r\n
@@ -177,6 +178,7 b' Restart server with support for API serv'
   >     user-agent: test
   > EOF
   using raw connection to peer
+  s> setsockopt(6, 1, 1) -> None (py3 !)
   s>     GET /api/ HTTP/1.1\r\n
   s>     Accept-Encoding: identity\r\n
   s>     user-agent: test\r\n
@@ -200,6 +202,7 b' Accessing an unknown API yields a 404'
   >     user-agent: test
   > EOF
   using raw connection to peer
+  s> setsockopt(6, 1, 1) -> None (py3 !)
   s>     GET /api/unknown HTTP/1.1\r\n
   s>     Accept-Encoding: identity\r\n
   s>     user-agent: test\r\n
@@ -222,6 +225,7 b' Accessing a known but not enabled API yi'
   >     user-agent: test
   > EOF
   using raw connection to peer
+  s> setsockopt(6, 1, 1) -> None (py3 !)
   s>     GET /api/exp-http-v2-0003 HTTP/1.1\r\n
   s>     Accept-Encoding: identity\r\n
   s>     user-agent: test\r\n
@@ -255,6 +259,7 b' Restart server with support for HTTP v2 '
   >     user-agent: test
   > EOF
   using raw connection to peer
+  s> setsockopt(6, 1, 1) -> None (py3 !)
   s>     GET /api HTTP/1.1\r\n
   s>     Accept-Encoding: identity\r\n
   s>     user-agent: test\r\n
@@ -276,6 +281,7 b' Restart server with support for HTTP v2 '
   >     user-agent: test
   > EOF
   using raw connection to peer
+  s> setsockopt(6, 1, 1) -> None (py3 !)
   s>     GET /api/ HTTP/1.1\r\n
   s>     Accept-Encoding: identity\r\n
   s>     user-agent: test\r\n