tests: conditionalize output in test-ssh.t with chg+py3

Because of our wrapping around sys.std* and python3 internal buffering, the
output order changes. The change in order seems like harmless because just few
lines above the same command is run which results in same output.

This makes `test-ssh.t` works with --chg on python 3.

Differential Revision: https://phab.mercurial-scm.org/D9502

tests/test-ssh.t

@@ -331,9 +331,10 b' try again with remote chg, which should '
   remote: adding changesets
   remote: adding manifests
   remote: adding file changes
+  remote: added 1 changesets with 1 changes to 1 files (py3 !)
   remote: KABOOM
   remote: KABOOM IN PROCESS
-  remote: added 1 changesets with 1 changes to 1 files
+  remote: added 1 changesets with 1 changes to 1 files (no-py3 !)
 
 #endif