patch 9.0.2082: test_channel may fail because of IPv6 config issue

Problem:  test_channel may fail because of IPv6 config issues
Solution: Catch and skip the test, if getaddrinfo() fails with
          'Address family not supported'

Mark tests as skipped when ch_open encounters E901

On some of the Debian build systems, the IPv6 channel tests fail because
`ch_open('[::1]:<port>', ...)` raises the error "E901: getaddrinfo() in
channel_open(): Address family for hostname not supported".

This appears to happen because getaddrinfo() can't perform the reverse
lookup for the ::1, which is a config issue on that system.  Therefore,
instead of reporting a test failure, mark the test as skipped due to the
bad network config

closes: #13473

Signed-off-by: James McCoy <jamessan@jamessan.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

Author: jamessan

src/testdir/shared.vim

@@ -113,6 +113,8 @@ func RunServer(cmd, testfunc, args)
     endif
 
     call call(function(a:testfunc), [port])
+  catch /E901.*Address family for hostname not supported/
+    throw 'Skipped: Invalid network setup ("' .. v:exception .. '" in ' .. v:throwpoint .. ')'
   catch
     call assert_report('Caught exception: "' . v:exception . '" in ' . v:throwpoint)
   finally

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2082,
 /**/
     2081,
 /**/