tests: Solaris grep doesn't add a trailing newline when it's missing

The bad-extension tests emits a list of not-loaded extensions, and pipes
that output through grep.  On Solaris, the test-output gets "(no-eol)"
appended because although the message has no trailing newline, GNU grep
adds it.  If we simply add the newline to the message, the problem goes
away for both versions of grep.

tests/test-bad-extension.t

@@ -39,7 +39,7 names of extensions failed to load can b
   > command = cmdutil.command(cmdtable)
   > @command('showbadexts', norepo=True)
   > def showbadexts(ui, *pats, **opts):
-  >     ui.write('BADEXTS: %s' % ' '.join(sorted(extensions.notloaded())))
+  >     ui.write('BADEXTS: %s\n' % ' '.join(sorted(extensions.notloaded())))
   > EOF
   $ hg --config extensions.badexts=showbadexts.py showbadexts 2>&1 | grep '^BADEXTS'
   BADEXTS: badext badext2